I still find Firefox to render a lot of pages incorrectly, due to most of them being coded with IE in mind. However, with the OPERA browser this isnt a problem, pages usually display correctly even if they are coded for IE specifically.
It is also fast, and has the same or more features than Firefox. Highly recommended!
http://www.opera.no
The Fastest Browser on Earth with
Pop-up blocker
Opera Mail with SPAM killer
IRC-compatible chat
Newsreader
RSS newsfeeds
Integrated Google search
Small-Screen Rendering (SSR)
...and much, much more...