The Stylish extension is my favorite Firefox/Flock add-on. Stylish lets you alter any site’s CSS on the fly. Even more cool – you don’t need to do the work! Just go to a web site (like MSNBC.COM pictured below) and click on the Stylish icon in the bottom right of the browser status bar. Select “Find Styles for this page”.
That’s how I found MSNBC – Clean. MSNBC Clean strips out the ads and centers the page, among other things. It makes the web site much easier to read.
There are plenty of styles available for most sites. GMail, Google Reader, MSH, Yahoo, etc. Drop dead easy to use -highly recommended!