Firefox, simply because it's both Open Source and high quality. The plugins are big boosts as well.I have my eye on Konqueror which does have a very nice rendering engine in KHTML (which was I think first to get full CSS1/2/3 support), and it looks like KHTML and WebKit will be becoming much closer again since the split (but there are no plans to merge the codebases fully), so improvements in one should filter across to the other before long. Plus, since Qt 4.4 will have webkit integrated it won't be long before a KPart for webkit appears making Konqueror able to easily switch between the two rendering engines.If the web browsing profile was a bit nicer, I would use Konqueror, but as it stands there are still fairly minor flaws which hold me back (such as not being able to have multiple home pages in tabs).