If you're new to emacs, check out this introductory tutorial!

I've tried to separate everything logically and document the purpose of every line. init.el acts as a kind of table of contents. It's a good idea to eventually go through init.el and the files under the customizations directory so that you know exactly what's going on.

Emacs has decent support for CSS, HTML, JS, and many other file types out of the box, but if you want better support, then have a look at my personal emacs config's init.el. It's meant to read as a table of contents. The emacs.d as a whole adds the following:

• Customizes js-mode and html editing
  • Sets indentation level to 2 spaces for JS
  • enables subword-mode so that M-f and M-b break on capitalization changes
  • Uses tagedit to give you paredit-like functionality when editing html
  • adds support for coffee mode
• Uses enh-ruby-mode for ruby editing. enh-ruby-mode is a little nicer than the built-in ruby-mode, in my opinion.
  • Associates many filenames and extensions with enh-ruby-mode (.rb, .rake, Rakefile, etc)
  • Adds keybindings for running specs
• Adds support for YAML and SCSS using the yaml-mode and scss-mode packages

In general, if you want to add support for a language then you should be able to find good instructions for it through Google. Most of the time, you'll just need to install the "x-lang-mode" package for it.