Every browser won't render every site correctly or at speed. That's why I keep a few browsers handy, in case I run into a site that isn't standards compliant; just switch browsers and keep going. FrontPage, for example, is notorious for generating web pages that comply with NO standards, and deliberately break Netscape browsers.
Any site that says any crap about "This site is best viewed with (fill in the blank)" is a site to avoid.
Yeah, I do this stuff for a living. Feh.
Hope this helps,