Doing web development on my local machine - a Vista box - I was wondering why page rendering was so slow. First I thought my web application was not well done. But then I figured out that the pages rendered lightning fast on IE 7. And again later, I experienced, that the web application rendered pretty fast even in Firefox, when published to the live server.

The change of the Firefox setting network.dns.disableIPv6 to true did the trick. (about:config)
Original: http://codepoetry.wordpress.com/2007/03/27/firefox-very-slow-on-localhost-connections-on-vista/