Chromium 17 and Konqueror 4.8 do not support MathML natively;
Safari 5.1 reportedly does. However, I sometimes find Chromium to
work better than Firefox on interactive sites that serve complex
web forms such as online banks, stores, and LinkedIn. I routinely
use both Firefox and Chromium. Update April 2013: Google Chrome 26
appears to work fine.
MathML may be displayed in Internet Explorer, but requires the
plugin. (Not tested.)