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• CSS Practice
• CSS3 Properties
• SCSS Interview Questions and Answers
• CSS Multiple Choice Questions

A CSS selector is the part of a CSS rule set that actually selects the content you want to style.

i) Universal Selector: The universal selector works like a wild card character, selecting all elements on a page. Every HTML page is built on content placed within HTML tags. Each set of tags represents an element on the page.

* {
   color: green;
   font-size: 20px;
   line-height: 25px;
}

ii) Element Type Selector: This selector match one or more HTML elements of the same name.

ul {
   list-style: none;
   border: solid 1px #ccc;
}

<ul>
  <li>Fish</li>
  <li>Apples</li>
  <li>Cheese</li>
</ul>

<div class="example">
  <p>Example paragraph text.</p>
</div>

<ul>
  <li>Water</li>
  <li>Juice</li>
  <li>Maple Syrup</li>
</ul>

iii) ID Selector: This selector matches any HTML element that has an ID attribute with the same value as that of the selector.

#container {
   width: 960px;
   margin: 0 auto;
}

<div id="container"></div>

iv) Class Selector: The class selector also matches all elements on the page that have their class attribute set to the same value as the class.

.box {
   padding: 20px;
   margin: 10px;
   width: 240px;
}

<div class="box"></div>

v) Descendant Combinator: The descendant selector or, more accurately, the descendant combinator lets you combine two or more selectors so you can be more specific in your selection method.

#container .box {
   float: left;
   padding-bottom: 15px;
}

This declaration block will apply to all elements that have a class of box that are inside an element with an ID of container. It’s worth noting that the .box element doesn’t have to be an immediate child: there could be another element wrapping .box, and the styles would still apply.

<div id="container">
  <div class="box"></div>

  <div class="box-2"></div>
</div>

<div class="box"></div>

vi) Child Combinator: A selector that uses the child combinator is similar to a selector that uses a descendant combinator, except it only targets immediate child elements.

#container > .box {
   float: left;
   padding-bottom: 15px;
}

The selector will match all elements that have a class of box and that are immediate children of the #container element. That means, unlike the descendant combinator, there can’t be another element wrapping .box—it has to be a direct child element.

<div id="container">
  <div class="box"></div>

  <div>
    <div class="box"></div>
  </div>
</div>

vii) General Sibling Combinator: A selector that uses a general sibling combinator matches elements based on sibling relationships. The selected elements are beside each other in the HTML.

h2 ~ p {
   margin-bottom: 20px;
}

In this example, all paragraph elements (<p>) will be styled with the specified rules, but only if they are siblings of <h2> elements. There could be other elements in between the <h2> and <p>, and the styles would still apply.

<h2>Title</h2>
<p>Paragraph example.</p>
<p>Paragraph example.</p>
<p>Paragraph example.</p>
<div class="box">
  <p>Paragraph example.</p>
</div>

viii) Adjacent Sibling Combinator: A selector that uses the adjacent sibling combinator uses the plus symbol (+), and is almost the same as the general sibling selector. The difference is that the targeted element must be an immediate sibling, not just a general sibling.

p + p {
   text-indent: 1.5em;
   margin-bottom: 0;
}

In this example will apply the specified styles only to paragraph elements that immediately follow other paragraph elements. This means the first paragraph element on a page would not receive these styles. Also, if another element appeared between two paragraphs, the second paragraph of the two wouldn’t have the styles applied.

<h2>Title</h2>
<p>Paragraph example.</p>
<p>Paragraph example.</p>
<p>Paragraph example.</p>

<div class="box">
  <p>Paragraph example.</p>
  <p>Paragraph example.</p>
</div>

ix) Attribute Selector: The attribute selector targets elements based on the presence and/or value of HTML attributes, and is declared using square brackets

input[type="text"] {
   background-color: #444;
   width: 200px;
}

<input type="text">

The attribute selector can also be declared using just the attribute itself, with no value, like this:

input[type] {
   background-color: #444;
   width: 200px;
}

x) Pseudo-class: A pseudo-class uses a colon character to identify a pseudo-state that an element might be in—for example, the state of being hovered, or the state of being activated.

a:hover {
   color: red;
}

xi) Pseudo-element: A CSS pseudo-element is used to style specified parts of an element. For example, it can be used to:

• Style the first letter, or line, of an element
• Insert content before, or after, the content of an element

<!DOCTYPE html>
<html>
  <head>
    <style>
      p::first-line {
        color: #ff0000;
        font-variant: small-caps;
      }

      p::first-letter {
        color: #ff0000;
        font-size: xx-large;
      }

      h1::before {
        content: url(smiley.gif);
      }

      h1::after {
        content: url(smiley.gif);
      }

      ::selection {
        color: red;
        background: yellow;
      }
    </style>
  </head>
<body>
  <p>Lorem Ipsum is simply dummy text of the printing and typesetting industry.
  Lorem Ipsum has been the industry\'s standard dummy text ever since the 1500s,
  <h1>when an unknown printer took a galley of type and scrambled it to make a
  type specimen book.<h1></p>
</body>
</html>

Live Example

Contextual selector addresses specific occurrence of an element. It is a string of individual selectors separated by white space (search pattern), where only the last element in the pattern is addressed providing it matches the specified contex.

It also check the context of the class in the html tree, assigning the style to the element through a specific route, taking into account the order of depth in the tree.

Example:

table p { property: value; } 

A pseudo-class is a selector that assists in the selection of something that cannot be expressed by a simple selector, for example :hover. A pseudo-element however allows us to create items that do not normally exist in the document tree, for example ::after.

Pseudo-classes

Pseudo-classes select regular elements but under certain conditions, like when their position relative to siblings or when they’re under a particular state. Here is a list of pseudo-classes in CSS3:

a) Dynamic pseudo-classes

• :link
• :visited
• :hover
• :active
• :focus

b) UI element states pseudo-classes

• :enabled
• :disabled
• :checked

c) Structural pseudo-classes

• :first-child
• :nth-child(n)
• :nth-last-child(n)
• :nth-of-type(n)
• :nth-last-of-type(n)
• :last-child
• :first-of-type
• :last-of-type
• :only-child
• :only-of-type
• :root
• :empty

d) Other pseudo-classes

:not(x) :target :lang(language)

Pseudo-elements

Pseudo-elements effectively create new elements that are not specified in the markup of the document and can be manipulated much like a regular element.

• ::before
• ::after
• ::first-letter
• ::first-line
• ::selection

A combinator is the character in a selector that connects two selectors together. There are four types of combinators.

a) Descendant Combinator (space): The descendant selector matches all elements that are descendants of a specified element.

The following example selects all <p> elements inside <div> elements:

div p {
  background-color: yellow;
}

b) Child Combinator (>): The child selector selects all elements that are the children of a specified element.

The following example selects all <p> elements that are children of a <div> element:

div > p {
  background-color: yellow;
}

c) Adjacent Sibling Combinator (+): The adjacent sibling selector selects all elements that are the adjacent siblings of a specified element.

The following example selects all <p> elements that are placed immediately after <div> elements:

div + p {
  background-color: yellow;
}

d) General Sibling Combinator (~): The general sibling selector selects all elements that are siblings of a specified element.

The following example selects all <p> elements that are siblings of <div> elements:

div ~ p {
  background-color: yellow;
}

In the CSS, a class selector is a name preceded by a full stop (“.”) and an ID selector is a name preceded by a hash character (“#”). The difference between an ID and a class is that an ID can be used to identify one element, whereas a class can be used to identify more than one.

#top {
    background-color: #ccc;
    padding: 20px
}

.intro {
    color: red;
    font-weight: bold;
}

<div id="top">

<h1>Chocolate curry</h1>
<p class="intro">This is my recipe for making curry purely with chocolate</p>
<p class="intro">Mmm mm mmmmm</p>

</div>

• CSS Grid Layout is a two-dimensional system, meaning it can handle both columns and rows, unlike flexbox which is largely a one-dimensional system (either in a column or a row).
• A core difference between CSS Grid and Flexbox is that — CSS Grid’s approach is layout-first while Flexbox’ approach is content-first. If you are well aware of your content before making layout, then blindly opt for Flexbox and if not, opt for CSS Grid.
• Flexbox layout is most appropriate to the components of an application (as most of them are fundamentally linear), and small-scale layouts, while the Grid layout is intended for larger-scale layouts which aren’t linear in their design.
• If you only need to define a layout as a row or a column, then you probably need flexbox. If you want to define a grid and fit content into it in two dimensions — you need the grid.

Live Example

The BEM (Block Element Modifier) methodology is a naming convention for CSS classes in order to keep CSS more maintainable by defining namespaces to solve scoping issues. A Block is a standalone component that is reusable across projects and acts as a "namespace" for sub components (Elements). Modifiers are used as flags when a Block or Element is in a certain state or is different in structure or style.

/* block component */
.block {
}

/* element */
.block__element {
}

/* modifier */
.block__element--modifier {
}

Example

.button {
	display: inline-block;
	border-radius: 3px;
	padding: 7px 12px;
	border: 1px solid #D5D5D5;
	background-image: linear-gradient(#EEE, #DDD);
	font: 700 13px/18px Helvetica, arial;
}
.button--state-success {
	color: #FFF;
	background: #569E3D linear-gradient(#79D858, #569E3D) repeat-x;
	border-color: #4A993E;
}
.button--state-danger {
	color: #900;
}

<button class="button">
	Normal button
</button>
<button class="button button--state-success">
	Success button
</button>
<button class="button button--state-danger">
	Danger button
</button>

Benefits

• Modularity: Block styles are never dependent on other elements on a page, so you will never experience problems from cascading.
• Reusability: Composing independent blocks in different ways, and reusing them intelligently, reduces the amount of CSS code that you will have to maintain.
• Structure: BEM methodology gives your CSS code a solid structure that remains simple and easy to understand.

CSS sprites combine multiple images into one single larger image. It is a commonly-used technique for icons.

Advantages:

• Reduce the number of HTTP requests for multiple images (only one single request is required per spritesheet). But with HTTP2, loading multiple images is no longer much of an issue.

• Advance downloading of assets that won't be downloaded until needed, such as images that only appear upon :hover pseudo-states. Blinking wouldn't be seen.

• When you have multiple images/ icons, browser makes separate call to the server for each one of them. sprite is a technique to combine all/ some of them (usually similar one in terms of type of image. For example, you will put jpg in one sprite) in one image. To display the icon you set height, width and background position.

Alternatives:

• Data URIs - allow you to embed the image data directly into a stylesheet. This avoids additional HTTP requests for images, making it essentially the same thing as a sprite, without the fancy positioning.
• Icon Fonts
• SVGs

The float CSS property places an element on the left or right side of its container, allowing text and inline elements to wrap around it.

Syntax

/* Keyword values */
float: left;
float: right;
float: none;
float: inline-start;
float: inline-end;

/* Global values */
float: inherit;
float: initial;
float: unset;

Property Values

Example:

section {
  border: 1px solid blue;
  width: 100%;
  float: left;
}

div {
  margin: 5px;
  width: 50px;
  height: 150px;
}

.left {
  float: left;
  background: pink;
}

.right {
  float: right;
  background: cyan;
}

<section>
  <div class="left">1</div>
  <div class="left">2</div>
  <div class="right">3</div>
  <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.
     Morbi tristique sapien ac erat tincidunt, sit amet dignissim
     lectus vulputate. Donec id iaculis velit. Aliquam vel
     malesuada erat. Praesent non magna ac massa aliquet tincidunt
     vel in massa. Phasellus feugiat est vel leo finibus congue.</p>
</section>

The pose-to-pose option is to create a few keyframes throughout the sequence, and then fill in the gaps later. Filling in these gaps is known as tweening. It is the process of generating intermediate frames between two images. It gives the impression that the first image has smoothly evolved into the second one. In CSS3, Transforms (matrix, translate, rotate, scale etc.) module can be used to achieve tweening.

Example:

p {
  animation-duration: 3s;
  animation-name: slidein;
}

@keyframes slidein {
  from {
    margin-left: 100%;
    width: 300%; 
  }

  to {
    margin-left: 0%;
    width: 100%;
  }
}

• visibility: hidden simply hides the element but it will occupy space and affect the layout of the document.
• display: none removes the element from the normal layout flow (causes DOM reflow). It will not affect the layout of the document nor occupy space.

Reflow is the name of the web browser process for re-calculating the positions and geometries of elements in the document, for the purpose of re-rendering part or all of the document.

Reflow occurs when

• insert, remove or update an element in the DOM
• modify content on the page, e.g. the text in an input box
• move a DOM element
• animate a DOM element
• take measurements of an element such as offsetHeight or getComputedStyle
• change a CSS style
• change the className of an element
• add or remove a stylesheet
• resize the window
• scroll

Minimizing browser reflow

• Reduce unnecessary DOM depth. Changes at one level in the DOM tree can cause changes at every level of the tree - all the way up to the root, and all the way down into the children of the modified node. This leads to more time being spent performing reflow.
• Minimize CSS rules, and remove unused CSS rules.
• If you make complex rendering changes such as animations, do so out of the flow. Use position-absolute or position-fixed to accomplish this.
• Avoid unnecessary complex CSS selectors - descendant selectors in particular - which require more CPU power to do selector matching.

The z-index helps specify the stack order of positioned elements that may overlap one another. The z-index default value is zero, and can take on either a positive or negative number. An element with a higher z-index is always stacked above than a lower index.

z-index can take the following values:

• Auto: Sets the stack order equal to its parents.
• Number: Orders the stack order.
• Initial: Sets this property to its default value (0).
• Inherit: Inherits this property from its parent element.

Live Example

• absolute, place an element exactly where you want to place it. absolute position is actually set relative to the element's parent. if no parent available then relatively place to the page itself (it will default all the way back up to the element).

• relative, means "relative to itself". Setting position: relative; on an element and no other positioning attributes, it will no effect on it's positioning. It allows the use of z-index on the element and it limits the scope of absolutely positioned child elements. Any child element will be absolutely positioned within that block.

• fixed, element is positioned relative to viewport or the browser window itself. viewport doesn't changed if you scroll and hence fixed element will stay right in the same position.

• static default for every single page element. The only reason you would ever set an element to position: static is to forcefully-remove some positioning that got applied to an element outside of your control.

• sticky - Sticky positioning is a hybrid of relative and fixed positioning. The element is treated as relative positioned until it crosses a specified threshold, at which point it is treated as fixed positioned.

Live Example

a) Block Elements
The block elements always start on a new line. They will also take space of an entire row or width. List of block elements are <p>, <h1>, <div>, <header>.

Example:

<p>
  Lorem ipsum dolor sit amet consectetur adipisicing elit. Unde autem,
  consequatur deleniti nobis beatae quo dolore nemo corporis. Ad delectus
  dignissimos pariatur illum eveniet dolor rem eius laborum sed iure!
</p>

<p>
  Lorem ipsum dolor sit amet consectetur adipisicing elit. Unde autem,
  consequatur deleniti nobis beatae quo dolore nemo corporis. Ad delectus
  dignissimos pariatur illum eveniet dolor rem eius laborum sed iure!
</p>

b) Inline Elements
Inline elements don't start on a new line, they appear on the same line as the content and tags beside them. Some examples of inline elements are <a>, <span> , <strong>, and <img> tags.

When it comes to margins and padding, browsers treat inline elements differently. You can add space to the left and right on an inline element, but you cannot add height to the top or bottom padding or margin of an inline element.

Example:

<a href="#">Link</a>
<img src="https://picsum.photos/30" />
<span>Span</span>
<strong>Strong Player</strong>

c) Inline-Block Elements
Inline-block elements are similar to inline elements, except they can have padding and margins added on all four sides. One common use for using inline-block is for creating navigation links horizontally. Some examples of inline-block elements are <input>, <button>, <select>, <textarea> etc.

input {
  width: 300px;
  height: 50px;
}

button {
  width: 100px;
  height: 50px;
  margin-top: 20px;
}

<input type="text" /> <button>Submit</button>

Live Example

CSS counters let you adjust the appearance of content based on its location in a document. To use a CSS counter, it must first be initialized to a value with the counter-reset property (0 by default). The same property can also be used to change its value to any specific number. Once initialized, a counter's value can be increased or decreased with counter-increment. The counter's name must not be "none", "inherit", or "initial"; otherwise the declaration is ignored.

body {
  counter-reset: section;   /* Set a counter named 'section', and its initial value is 0. */
}

h3::before {
  counter-increment: section;   /* Increment the value of section counter by 1 */
  content: "Section " counter(section) ": ";  /* Display the word 'Section ', the value of 
                                                 section counter, and a colon before the content
                                                 of each h3 */
}

<h3>Introduction</h3>
<h3>Body</h3>
<h3>Conclusion</h3>

CSS Counter Properties

Live Example

• px gives fine grained control and maintains alignment because 1 px or multiple of 1 px is guaranteed to look sharp. px is not cascade, this means if parent font-size is 20px and child 16px. child would be 16px.

• em maintains relative size. you can have responsive fonts. em is the width of the letter 'm' in the selected typeface. However, this concept is tricky. 1em is equal to the current font-size of the element or the browser default. if u sent font-size to 16px then 1em = 16px. The common practice is to set default body font-size to 62.5% (equal to 10px). em is cascade

• % sets font-size relative to the font size of the body. Hence, you have to set font-size of the body to a reasonable size. this is easy to use and does cascade. for example, if parent font-size is 20px and child font-size is 50%. child would be 10px.

• pt(points) are traditionally used in print. 1pt = 1/72 inch and it is fixed-size unit.

1. Pseudo Element: A CSS pseudo-element is used to style specified parts of an element.

For example, it can be used to:

• Style the first letter, or line, of an element
• Insert content before, or after, the content of an element

CSS Pseudo Elements

2. Pseudo-classes: A pseudo-class is used to define a special state of an element.

For example, it can be used to:

• Style an element when a user mouses over it
• Style visited and unvisited links differently
• Style an element when it gets focus

CSS Pseudo Classes

The CSS box model is a rectangular layout paradigm for HTML elements that consists of the following:

• Content: The content of the box, where text and images appear
• Padding: A transparent area surrounding the content (i.e., the amount of space between the border and the content)
• Border: A border surrounding the padding (if any) and content
• Margin: A transparent area surrounding the border (i.e., the amount of space between the border and any neighboring elements)

/* top   right  bottom left  */
padding: 25px  50px   75px   100px;

/* same padding on all 4 sides: */
padding: 25px;

/* top/bottom padding 25px; right/left padding 50px */
padding: 25px 50px;

/* top padding 25px; right/left padding 50px; bottom padding 75px */
padding: 25px 50px 75px;

Live Example

• cm centimeters
• em elements (i.e., relative to the font-size of the element; e.g., 2 em means 2 times the current font size)
• in inches
• mm millimeters
• pc picas (1 pc = 12 pt = 1/6th of an inch)
• pt points (1 pt = 1/72nd of an inch)
• px pixels (1 px = 1/96th of an inch)

• Every <a> element whose href attribute value begins with “https”.

  a[href^="https"]

• Every <a> element whose href attribute value ends with “.pdf”.

  a[href$=".pdf"]

• Every <a> element whose href attribute value contains the substring “css”.

  a[href*="css"]

The box-sizing CSS property sets how the total width and height of an element is calculated.

• content-box: the default width and height values apply to the element's content only. The padding and border are added to the outside of the box.
• padding-box: Width and height values apply to the element's content and its padding. The border is added to the outside of the box. Currently, only Firefox supports the padding-box value.
• border-box: Width and height values apply to the content, padding, and border.
• inherit: inherits the box sizing of the parent element.

Example:

box-sizing: content-box;
width: 100%;
border: solid rgb(90,107,204) 10px;
padding: 5px;

• RGB (Red/Green/Blue) is a color model.

p {
  color: rgba(37, 84, 127, 1);
}

• HEX (Hexadecimal color values)

p {
  color: #25547f;
}

• HSLa (Hue Saturation Lightness alpha)

p {
  color: hsla(209, 55%, 32%, 1);
}

Pre-processors extend CSS with variables, operators, interpolations, functions, mixins and many more other usable assets. After development, these specific files are compiled into regular CSS that any browser can understand. Pre-processor help writing reusable, easily maintainable and extensible codes in CSS.

CSS preprocessors

• SASS (SCSS)
• LESS
• Stylus
• PostCSS

Advantages:

• CSS is made more maintainable.
• Easy to write nested selectors.
• Variables for consistent theming. Can share theme files across different projects.
• Mixins to generate repeated CSS.
• Splitting your code into multiple files. CSS files can be split up too but doing so will require an HTTP request to download each CSS file.

1. Resetting: CSS resets aim to remove all built-in browser styling. For example margins, paddings, font-sizes of all elements are reset to be the same. You will have to redeclare styling for common typographic elements.

Example

html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, 
acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, 
sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, 
caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed,  figure, figcaption, 
footer, header, hgroup,  menu, nav, output, ruby, section, summary, time, mark, audio, video {  
   margin: 0;  
   padding: 0;  
   border: 0;  
   font-size: 100%;  
   font: inherit;  
   vertical-align: baseline; 
}

2. Normalizing: Normalize CSS aims to make built-in browser styling consistent across browsers. It also corrects bugs for common browser dependencies.

Example

/* 
  Correct the font size and margin on `h1` elements within `section`  
  and `article` contexts in Chrome, Firefox, and Safari.
*/
 h1 {  font-size: 2em;  margin: 0.67em 0;}

The clear property specifies what elements can float beside the cleared element and on which side.

Example

div {
  clear: left;
}

Floats, absolutely positioned elements, block containers (such as inline-blocks, table-cells, and table-captions) that are not block boxes, and block boxes with 'overflow' other than 'visible' (except when that value has been propagated to the viewport) establish new block formatting contexts for their contents.

In a block formatting context, each box's left outer edge touches the left edge of the containing block (for right-to-left formatting, right edges touch)

A BFC is an HTML box that satisfies at least one of the following conditions:

• The value of float is not none.
• The value of position is neither static nor relative.
• The value of display is table-cell, table-caption, inline-block, flex, or inline-flex.
• The value of overflow is not visible.

In a BFC, each box's left outer edge touches the left edge of the containing block (for right-to-left formatting, right edges touch). Vertical margins between adjacent block-level boxes in a BFC collapse.

Live Example

Yes. overflow property deals with the content if content size exceeds the allocated size for the content. You can make extra content visible, hidden, scroll or auto (viewport default behavior).

• Use a separate style sheet that only loads when that specific browser is being used. This technique requires server-side rendering though.
• Use autoprefixer to automatically add vendor prefixes to your code.
• Use Reset CSS or Normalize.css.

/*Example: 01*/
.box-shadow {
  background-color: red;
  background-image: url(gradient-slice.png);
  background-image: -webkit-linear-gradient(top right, #A60000, #FFFFFF); /*Chrome and Safari*/
  background-image: -moz-linear-gradient(top right, #A60000, #FFFFFF); 	  /*Firefox*/
  background-image: -ms-linear-gradient(top right, #A60000, #FFFFFF);     /*Internet Explorer*/
  background-image: -o-linear-gradient(top right, #A60000, #FFFFFF);      /*Opera*/
  background-image: linear-gradient(top right, #A60000, #FFFFFF);
}

/*Example: 02*/
.box {
	-moz-border-radius: 15px;    /* Firefox */
	-webkit-border-radius: 15px; /* Safari and Chrome */
	border-radius: 15px;
}

Technique: 01

h1#technique-one {
  width: 250px;
  height: 25px;
  background-image: url(logo.gif);
}
h1#technique-one span {
  display: none;
}

<h1 id="technique-one">
  <span>CSS-Tricks</span>
</h1>

Technique: 02

h1.technique-two {
  width: 2350px; 
  height: 75px;
  background: url("images/header-image.jpg") top right;
  margin: 0 0 0 -2000px;
}

<h1 class="technique-two">
  CSS-Tricks
</h1>

Technique: 03

h1.technique-three {
  width: 350px; 
  height: 75px;
  background: url("images/header-image.jpg");
  text-indent: -9999px;
}

<h1 class="technique-three">
  CSS-Tricks
</h1>

Technique: 04

h1.technique-four {
	width: 350px; 
  height: 75px;
	background: url("images/header-image.jpg");
	text-indent: -9999px;
}

<h1 class="technique-four">
  <a href="#">
    <img src="images/header-image.jpg" alt="CSS-Tricks" />
  </a>
</h1>

Technique: 05

h1.technique-five {
	width: 350px; 
  height: 75px;
	background: url("images/header-image.jpg");
}
h1.technique-five span {
  display: none;
}

<h1 class="technique-five">
  <img src="images/blank.gif" alt="CSS-Tricks" />
  <span>CSS-Tricks</span>
</h1>

Technique: 06

h1.technique-six {
	width: 350px;
	padding: 75px 0 0 0;
	height: 0;
	background: url("images/header-image.jpg") no-repeat;
	overflow: hidden;
}

<h1 class="technique-six">
  CSS-Tricks
</h1>

Technique: 07

h1.technique-seven {
	width: 350px; 
  height: 75px;
	background: url("images/header-image.jpg") no-repeat;
}
h1.technique-seven span {
  display: block;
  width: 0;
  height: 0;
  overflow: hidden;
}

<h1 class="technique-seven">
	<span>CSS-Tricks</span>
</h1>

Technique: 08

h1.technique-eight {
	width: 350px; 
  height: 75px;
	position: relative;
}
h1.technique-eight span {
  background: url("images/header-image.jpg");
  position: absolute;
  width: 100%;
  height: 100%;
}

<h1 class="technique-eight">
  <span></span>CSS-Tricks
</h1>

Technique: 09

h1.technique-nine {
  width: 350px; 
  height: 75px;
  background: url("images/header-image.jpg") no-repeat;
  font-size: 1px;
  color: white;
}

<h1 class="technique-nine">
  CSS-Tricks
</h1>

• Graceful degradation: The practice of building an application for modern browsers while ensuring it remains functional in older browsers.
• Progressive enhancement: The practice of building an application for a base level of user experience, but adding functional enhancements when a browser supports it.
• caniuse: to check for feature support.
• Autoprefixer: for automatic vendor prefix insertion.
• Feature detection: using Modernizr.
• CSS Feature queries: using @support

These techniques are related to accessibility (a11y).

• visibility: hidden: However, the element is still in the flow of the page, and still takes up space.
• width: 0; height: 0: Make the element not take up any space on the screen at all, resulting in not showing it.
• position: absolute; left: -99999px: Position it outside of the screen.
• text-indent: -9999px: This only works on text within the block elements.
• Metadata: For example by using Schema.org, RDF, and JSON-LD.
• WAI-ARIA: A W3C technical specification that specifies how to increase the accessibility of web pages.

Media queries are useful when you want to modify your site or app depending on a device's general type (such as print vs. screen) or specific characteristics and parameters (such as screen resolution or browser viewport width). It uses the @media rule to include a block of CSS properties only if a certain condition is true.

Media Types

Media Features

Example:

@media print {
  body { font-size: 10pt; }
}

@media screen {
  body { font-size: 13px; }
}

@media only screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}

/* Nested within another conditional at-rule */
@supports (display: flex) {
  @media screen and (min-width: 900px) {
    article {
      display: flex;
    }
  }
}

/* Extra small devices (phones, 600px and down) */
@media only screen and (max-width: 600px) { }

/* Small devices (portrait tablets and large phones, 600px and up) */
@media only screen and (min-width: 600px) { }

/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) { }

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) { }

/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) { }

It hide style sheets from older user agents.

Browser's Viewport

Use @font-face and define font-family for different font-weights.

Browsers match selectors from rightmost (key selector) to left. Browsers filter out elements in the DOM according to the key selector and traverse up its parent elements to determine matches. The shorter the length of the selector chain, the faster the browser can determine if that element matches the selector.

For example with this selector p span, browsers firstly find all the <span> elements and traverse up its parent all the way up to the root to find the <p> element. For a particular <span>, as soon as it finds a <p>, it knows that the <span> matches and can stop its matching.

@import: allows to load stylesheet by using a path (uri) representing the location of the file.

/* By default, include the "light" color theme for syntax highlighting */
@import "cdn.com/atom-one-light.min.css";
/* And if you’re in dark mode, have those rules superseded via a different stylesheet */
@media (prefers-color-scheme: dark) {
  @import "cdn.com/atom-one-dark.min.css";
}

matchMedia(): Using matchMedia lets you execute blocks of JavaScript only when a certain media query condition is met. This means you can just write out the CSS when and if the query is true:

if (window.matchMedia('screen and (min-width: 600px)')) {
  document.write('<link rel="stylesheet" href="css/small.css">');
}

• Make every element in the document include the padding and border in the element's inner dimensions; making it easier to reason about the layout of elements on the page.
• By default, elements have box-sizing: content-box applied, and only the content size is being accounted for.
• box-sizing: border-box changes how the width and height of elements are being calculated, border and padding are also being included in the calculation.
• The height of an element is now calculated by the content's height + vertical padding + vertical border width.
• The width of an element is now calculated by the content's width + horizontal padding + horizontal border width.
• Taking into account paddings and borders as part of our box model resonates better with how designers actually imagine content in grids.

The display property specifies the display behavior (the type of rendering box) of an element.
Example:

p.ex1 {display: none;}
p.ex2 {display: inline;}
p.ex3 {display: block;}
p.ex4 {display: inline-block;}

Property Values

1) Responsive design uses CSS media queries to change styles based on the target device such as display type, width, height, etc., and only one of these is necessary for the site to adapt to different screens.

Responsive doesn’t offer as much control as adaptive, but takes much less work to both build and maintain. Responsive layouts are also fluid and whilst adaptive can and do use percentages to give a more fluid feel when scaling, these can again cause a jump when a window is resized.

2) Adaptive design uses static layouts based on breakpoints which don't respond once they\’re initially loaded. Adaptive works to detect the screen size and load the appropriate layout for it. Generally adaptive site uses six common screen widths:

• 320 px
• 480 px
• 760 px
• 960 px
• 1200 px
• 1600 px

Adaptive is useful for retrofitting an existing site in order to make it more mobile-friendly. This allows you to take control of the design and develop for specific, multiple viewports.

In order to have crisp, good-looking graphics that make the best of retina displays we need to use high resolution images whenever possible. However using always the highest resolution images will have an impact on performance as more bytes will need to be sent over the wire.

To overcome this problem, we can use responsive images, as specified in HTML5. It requires making available different resolution files of the same image to the browser and let it decide which image is best, using the html attribute srcset and optionally sizes, for instance:

<div responsive-background-image>  
  <img src="/images/foo.png" alt="bar" srcset="/images/foo.png 2x" />
</div>

<!-- It enable the browser to use a medium and large image based on 
     the sizes of the image in the viewport
-->
<img
  src="/images/foo.png"
  alt="bar"
  srcset="/images/foo-medium.png 1024w,
               /images/foo-large.png 2048w,
               /images/foo.png 800w"
/>

The browsers which does not support HTML5's srcset (i.e. IE11) will ignore it and uses src instead. If we really need to support IE11 and we want to provide this feature for performance reasons, we can use a JavaScript polyfill.

HTML5 picture Element

<picture>
   <source media="(min-width: 1024px)" srcset="foo-large.jpg  1024w, foo-medium.jpg 640w" sizes="50vw" />
   <source srcset="[email protected] 2x, foo.jpg 1x" />
   <img src="foo.jpg" alt="Bar" />
</picture>

Retina Display Media Query

/* 1.25 dpr */
@media (-webkit-min-device-pixel-ratio: 1.25), (min-resolution: 120dpi) { 
    /* Retina-specific stuff here */
}

/* 1.3 dpr */
@media (-webkit-min-device-pixel-ratio: 1.3), (min-resolution: 124.8dpi) { 
    /* Retina-specific stuff here */
}

/* 1.5 dpr */
@media (-webkit-min-device-pixel-ratio: 1.5), (min-resolution: 144dpi) { 
    /* Retina-specific stuff here */
}

translate() is a value of CSS transform. Changing transform or opacity does not trigger browser reflow or repaint but does trigger compositions; whereas changing the absolute positioning triggers reflow. transform causes the browser to create a GPU layer for the element but changing absolute positioning properties uses the CPU. Hence translate() is more efficient and will result in shorter paint times for smoother animations.

When using translate(), the element still occupies its original space (sort of like position: relative), unlike in changing the absolute positioning.

Example:

If we combine position:relative with one of the offset properties top, bottom, left or right the element will be moved from its original place in the layout whilst preserving the space in the document it once occupied. The element will be moved on to a new layer and its “layer order” or its stacking order can then be controlled with the z-index property.

.thing {
  position: relative;
  top: 100px;
  left: 50px;
}

In the above example the element will be moved 100px away from the top and 50px away from the left of its original position.

When using transform:translate(x,y) we get a very similar visual result to using relative position. The same result as above could be achieved with the following snippet:

.thing {
  transform: translate(50px, 100px);
}

In this case, we are translating the coordinates of the element by 50px along the x-axis and 100px along the y-axis. The end result is visually the same as the previous position example.

• False

<em>: The HTML <em> tag represents stress emphasis of its contents.

<em>Emphasized content...</em>

<b>: The <b> tag specifies bold text without any extra importance.

<p>This is normal text - <b>and this is bold text</b>.</p>

<abbr>: The HTML Abbreviation element (<abbr>) represents an abbreviation or acronym; the optional title attribute can provide an expansion or description for the abbreviation.

The <abbr title="World Health Organization">WHO</abbr> was founded in 1948.

<nav>: The <nav> tag defines a set of navigation links.

<nav>
  <a href="/html/">HTML</a> |
  <a href="/css/">CSS</a> |
  <a href="/js/">JavaScript</a> |
  <a href="/jquery/">jQuery</a>
</nav>

<i>: The content of the <i> tag is usually displayed in italic.

<p>I looked at it and thought <i>This can't be real!</i></p>

<link>: The HTML <link> tag is used for defining a link to an external resource. It is placed in in the <head> section of the HTML document.

<head>
  <link rel="stylesheet" type="text/css" href="theme.css">
</head>

<strong>: The <strong> element is used to identify text that is of greater importance than the surrounding text. By default, all browsers render <strong> text in a bold typeface.

<strong>Strong text</strong>

<article>: The <article> tag specifies independent, self-contained content.

<article>
  <h1>Google Chrome</h1>
  <p>Google Chrome is a free, open-source web browser developed by Google, released in 2008.</p>
</article>

At-rules are CSS statements that instructs CSS how to behave. They begin with an at sign, @ followed by an identifier and includes everything up to the next semicolon, ; or the next CSS block, whichever comes first.

/* General structure */
@IDENTIFIER (RULE);

/* Example: tells browser to use UTF-8 character set */
@charset "utf-8";

As images being inline elements are treated same as texts, so there is a gap left, which can be removed by:

<figure>
  <img style="display: block" src="..." alt="">
</figure>

Progressive rendering is the name given to techniques used to improve the performance of a webpage (in particular, improve perceived load time) to render content for display as quickly as possible.

Examples:

• Lazy loading of images - Images on the page are not loaded all at once. JavaScript will be used to load an image when the user scrolls into the part of the page that displays the image.
• Prioritizing visible content (or above-the-fold rendering) - Include only the minimum CSS/content/scripts necessary for the amount of page that would be rendered in the users browser first to display as quickly as possible, you can then use deferred scripts or listen for the DOMContentLoaded/load event to load in other resources and content.
• Async HTML fragments - Flushing parts of the HTML to the browser as the page is constructed on the back end.

Making a website responsive means the some elements will respond by adapting its size or other functionality according to the device's screen size, typically the viewport width, through CSS media queries, for example, making the font size smaller on smaller devices.

@media (min-width: 601px) {
  .my-class {
    font-size: 24px;
  }
}
@media (max-width: 600px) {
  .my-class {
    font-size: 12px;
  }
}

A mobile-first strategy is also responsive, however it agrees we should default and define all the styles for mobile devices, and only add specific responsive rules to other devices later. Following the previous example:

.my-class {
  font-size: 12px;
}

@media (min-width: 600px) {
  .my-class {
    font-size: 24px;
  }
}

A mobile-first strategy has 2 main advantages:

• It's more performant on mobile devices, since all the rules applied for them don't have to be validated against any media queries.
• It forces to write cleaner code in respect to responsive CSS rules.

Live Example

Accessibility refers to how software or hardware combinations are designed to make a system accessible to persons with disabilities, such as:

• Visual impairment
• Hearing loss
• Limited dexterity

For example, a website developed with accessibility in mind might have text-to-speech capabilities or output for special braille hardware geared toward individuals with visual impairments.

1) UI or User Interface: is how a product or website is laid out and how you interact with it: Where the buttons are, how big the fonts are, and how menus are organized are all elements of UI.

2) UX or User Experience: is how you feel about using a product or a website. So, your love for the way the new Apple Watch looks or your excitement that there’s finally a tablet-sized iPhone to watch those Corgi videos you’re obsessed with are reflections of UX. So the new look of the Facebook news feed involves a change to UI, and the way you navigate that new page is the UX.

The font-family property is used to change the face of a font.

The font-style property is used to make a font italic or oblique.

The font-variant property is used to create a small-caps effect.

The font-weight property is used to increase or decrease how bold or light a font appears.

The letter-spacing property is used to add or subtract space between the letters that make up a word.

The word-spacing property is used to add or subtract space between the words of a sentence.

The text-indent property is used to indent the text of a paragraph.

The text-align property is used to align the text of a document.

The text-decoration property is used to underline, overline, and strikethrough text.

The text-transform property is used to capitalize text or convert text to uppercase or lowercase letters.

The list-style-type allows you to control the shape or appearance of the marker.

The keyword initial can be used to resets it to its default value, which is defined in the CSS specification of the given property.

A process of determining which css rule will be applied to an element. It actually determines which rules will take precedence. Inline style usually wins then ID then class value (or pseudo-class or attribute selector), universal selector (*) has no specificity. ID selectors have a higher specificity than attribute selectors.

Selector Types

The following list of selector types increases by specificity:

• Type selectors (e.g., h1) and pseudo-elements (e.g., ::before).
• Class selectors (e.g., .example), attributes selectors (e.g., [type="radio"]) and pseudo-classes (e.g., :hover).
• ID selectors (e.g., #example).

/*wins*/
a#a-02 { background-image : url(n.gif); }
a[id="a-02"] { background-image : url(n.png); }

Contextual selectors are more specific than a single element selector.The embedded style sheet is closer to the element to be styled. The last rule defined overrides any previous, conflicting rules.

p { color: red; background: yellow }
p { color: green } // wins

A class selector beats any number of element selectors.

.introduction {} //wins
html body div div h2 p {}

CSS Transitions allows to add an effect while changing from one style to another. You can set the which property you want to transition, duration, how you want to transit (linear, ease, ease-in, ease-out, cubic-bezier) and delay when transition will start.

CSS Transition Properties

Example:

div {
  width: 100px;
  height: 100px;
  background: red;
  -webkit-transition: width 2s; /* Safari prior 6.1 */
  transition: width 2s;
}

Live Example

The filter CSS property applies graphical effects like blur or color shift to an element. Filters are commonly used to adjust the rendering of images, backgrounds, and borders.

Example:

img {
  -webkit-filter: brightness(200%); /* Safari 6.0 - 9.0 */
  filter: brightness(200%);
}

Filter Functions

Both em and rem units are based on the font-size CSS property. The only difference is where they inherit their values from.

• em units inherit their value from the font-size of the parent element

.parent {
  font-size: 18px;
}
.child {
  font-size: 1.5em;
}

<div class="parent">
  I'm 15px
  <div class="child">
  I'm 30px, as expected
    <div class="child">
    I'm 60px, trouble starts!
      <div class="child">
      I'm 120px, now we're really in trouble!
      </div>
    </div>
  </div>
</div>

• rem units inherit their value from the font-size of the root element (html)

.html {
  font-size: 16px;
}
.parent {
  font-size: 15px;
}
.child-rem {
  font-size: 2rem;
}

<div class="parent">
  I'm 15px
  <div class="child-rem">
  I'm 32px, as expected
    <div class="child-rem">
    I'm 32px, yep!
      <div class="child-rem">
      I'm 32px, like clockwork!
      </div>
    </div>
  </div>
</div>

Note: In most browsers, the font-size of the root element is set to 16px by default.

It overrides the cascade and gives the style rule the highest precedence.

p {
    color: red !important;
}
#thing {
    color: green;
}

<p id="thing">Will be RED.</p>

<head>
    <link href="style1.css" rel="stylesheet">
</head>
<body>
    <p>Paragraph 1</p>
    <p>Paragraph 2</p>
    <link href="style2.css" rel="stylesheet">
</body>

• Yes

<head>
    <link href="style1.css" rel="stylesheet">
    <link href="style2.css" rel="stylesheet">
</head>

• No

1) Margin is applied to the outside of you element hence effecting how far your element is away from other elements.
2) Padding is applied to the inside of your element hence effecting how far your element's content is away from the border.

Also, using margin will not affect your element's dimensions whereas padding will make your elements dimensions (set height + padding) so for example if you have a 100x100px div with a 5 px padding, your div will actually be 105x105px

Note: Top/Bottom margins are collapsible: if you have a 20px margin at the bottom of an element and a 30px margin at the top of the next element, the margin between the two elements will be 30px rather than 50px. This does not apply to left/right margin or padding.

1. CSS3 Selectors

• Matches any element E whose attribute attr starts with the value val. In other words, the val matches the beginning of the attribute value.

E[attr^=val]
/* Example */
a[href^='http://sales.']{color: teal;}

• Matches any element E whose attribute attr ends in val. In other words, the val matches the end of the attribute value.

E[attr$=val]
/* Example */
a[href$='.jsp']{color: purple;}

• Matches any element E whose attribute attr matches val anywhere within the attribute. It is similar to E[attr~=val], except the val can be part of a word.

E[attr*=val]  
/* Example */
img[src*='artwork']{
        border-color: #C3B087 #FFF #FFF #C3B087;
}

2. Pseudo-classes
CSS2 supports user interaction pseudo-classes, namely :link, :visited, :hover, :active, and :focus.
A few more pseudo-class selectors were added in CSS3. One is the :root selector, which allows designers to point to the root element of a document.

  :root{overflow:auto;}

As a complement to the :first-child selector, the :last-child was added. With it one can select the last element named of a parent element.

  div.article > p:last-child{font-style: italic;}

A new user interaction pseudo-class selector was added, the :target selector.

<style>
  span.notice:target { font-size: 2em; font-style: bold; }
</style>

<a href='#section2'>Section 2</a>
<p id='section2'>...</p>

The negation pseudo-class selector, :not can be coupled with almost any other selector that has been implemented.

  img:not([border]){ border: 1; }

3. CSS3 Colors
The color keyword list has been extended in the CSS3 color module to include 147 additional keyword colors (that are generally well supported), CSS3 also provides us with a number of other options: HSL, HSLA, RGBA and Opacity.

div.halfopaque {
  background-color: rgb(0, 0, 0);
  opacity: 0.5;
  color: #000000;
}
div.halfalpha {
  background-color: rgba(0, 0, 0, 0.5);
  color: #000000;
}

4. Rounded Corners: border-radius

border-radius: 25px;

5 Drop Shadows

box-shadow: 2px 5px 0 0 rgba(72,72,72,1);

6. Text Shadow

text-shadow: topOffset leftOffset blurRadius color;

7. Linear Gradients

Syntax: background: linear-gradient(direction, color-stop1, color-stop2, ...);
/* Example */   
#grad {
  background: linear-gradient(to right, red , yellow);
}

8. Radial Gradients

Syntax : background: radial-gradient(shape size at position, start-color, ..., last-color);
/* Example */      
#grad {
  background: radial-gradient(red, yellow, green);
}//Default       
#grad {
  background: radial-gradient(circle, red, yellow, green);
}//Circle

9. Multiple Background Images
In CSS3, there’s no need to include an element for every background image; it provides us with the ability to add more than one background image to any element, even to pseudo-elements.

background-image:
url(firstImage.jpg),
url(secondImage.gif),
url(thirdImage.png);

CSS gradients are represented by the <gradient> data type, a special type of <image> made of a progressive transition between two or more colors. There are three types of gradients:

• linear (created with the linear-gradient() function),
• radial (created with radial-gradient()), and
• conic (created with the conic-gradient() function).

We can also create repeating gradients with the repeating-linear-gradient(), repeating-radial-gradient(), and repeating-conic-gradient() functions.

/* Example - 01: A basic linear gradient */
.simple-linear {
  background: linear-gradient(blue, pink);
}

/* Example - 02: Changing the direction */
.horizontal-gradient {
  background: linear-gradient(to right, blue, pink);
}

/* Example - 03: Diagonal gradients */
.diagonal-gradient {
  background: linear-gradient(to bottom right, blue, pink);
}

/* Example - 04: Using angles */
.angled-gradient {
  background: linear-gradient(70deg, blue, pink);
}

/* Example - 05: Creating hard lines */
.striped { 
   background: linear-gradient(to bottom left, cyan 50%, palegoldenrod 50%); 
}

The opacity CSS property sets the opacity of an element. Opacity is the degree to which content behind an element is hidden, and is the opposite of transparency.

div { background-color: lightblue; }
.light {
  opacity: 30%; /* Barely see the text over the background */
}
.medium {
  opacity: 60%; /* See the text more clearly over the background */
}
.heavy {
  opacity: 100%; /* See the text very clearly over the background */
}

<div class="light">You can barely see this.</div>
<div class="medium">This is easier to see.</div>
<div class="heavy">This is very easy to see.</div>

Inheritance is a concept in which the child class will inherit the properties of its parent class. It is used in CSS to define the hierarchy from the top level to the bottom level. Inherited properties can be overridden by the children class if the child uses the same name.

Example:

span {
  color: blue;
  border: 1px solid black;
}
.extra span {
  color: inherit;
}

The @supports query in CSS can be very useful to scan if the user's current browser has a certain feature. The @supports CSS at-rule lets you specify declarations that depend on a browser's support for one or more specific CSS features. This is called a feature query. The rule may be placed at the top level of your code or nested inside any other conditional group at-rule.

@supports (display: grid) {
  div {
    display: grid;
  }
}

@supports not (display: grid) {
  div {
    float: right;
  }
}

Cascade is a method of defining the weight (importance) of individual styling rules thus allowing conflicting rules to be sorted out should such rules apply to the same selector.

P {color: white ! important} /* increased weight */
P (color: black} /* normal weight */

Vendor prefixes are extensions to CSS standards that can be added to these features to prevent incompatibilities from arising when the standard is extended. CSS vendor prefixes for some common platforms are listed below.

• -webkit-: Android, Chrome, iOS, and Safari
• -moz-: Mozilla Firefox
• -ms-: Internet Explorer
• -o-: Opera