Konqueror! Well so I am told anyways. If I could get KDE to install in Debian I'd be able to tell you for sure. I had the same question as you just recently and have done a lot of research into it and Konqueror is what I could come up with. It already has java and flash support. 100 percent css1 support and 65 percent css2 support. Supposedly it is fast as hell too! Check it out, tell me what you think of it, I am interested to know your results!