As a web developer I'm also looking at the source code of web pages. Once of the things that makes this hard is that you have to look at the headers to see the locations of the CSS and javascript files. And then you need to go fetch of them individually. This is a slow and tedious process.

Then I came across the JSView plug-in for Firefox. It changed my life. Seriously. When you are viewing source, this plug-in make will go fetch all of the CSS and Javascript files for you automatically and show them. If you are a developer who is often viewing the source of web pages, you know what a pain this is, and you'll be amazed at what a difference this plug-in makes.