There are many good CSS editors for Linux. Basically, all you really need is a text editor that will perform syntax highlighting on CSS files. Some of the programs below are just simple text editors, while some offer additional features.
I recently mentioned that I like jEdit for Ruby on Rails. I added the Ruby plugin for jEdit (which can be installed directly through the jEdit plugin manager). There is also a plugin called SuperAbbrevs that allows you to create typing shortcuts for Ruby on Rails (or any other language). The screenshot below shows the Ruby documentation displayed on the right side of jEdit. The jEdit Ruby plugin also has a method completion feature but I couldn't get a clean screenshot of it.
Further experimentation with editors for Ruby on Rails led to the question "how do I change the default editor on Ubuntu?" All of my files were opening in gedit and to override it I had to right-click on my .rb and .rhtml files and then choose my desired editor.
I finally figured out how to quickly change Ubuntu's default text editor with Nautilus:
I spent many hours today trying to find a good editor on Ubuntu Linux for working with Ruby on Rails.
Emacs, gedit, and other editors were not working well for me. I was having problem with indentation and syntax highlighting with .rhtml files so I began investigating other editors for Ruby on Rails that would run on Ubuntu Dapper Drake.