Microsoft released Internet Explorer 9 on March 15. Faster, more secure, and far less cluttered than ever before, IE 9 is getting good reviews. IE 9 can be installed on Windows 7 and Vista only; XP users are out of luck. It's really time to change from XP.
Internet Explorer 9 can be downloaded from Microsoft or any number of download sites. For best performance use the 32-bit version of Internet Explorer. That goes for version 8, as well. http://windows.microsoft.com/en-us/internet-explorer/products/ie/home
Mozilla released Firefox 4 on March 22, with the same goals (see last post http://cathycom.blogspot.com/2011/03/firefox-4-now-ready-for-download.html).
The Browser Wars have been going on so long the various contenders seem to be merging. The Big Three (no, not Ford, Chrysler and GM) are Internet Explorer, Mozilla Firefox and Google Chrome. The new versions seem pretty much interchangeable. More than ever, personal preference will decide your default browser.
It's still a good idea to have at least two browsers installed, and running all three is quite acceptable. There are many web sites that perform differently in different browsers. One, two, three or more browsers of the same maker or different can be open at the same time, given enough system resources.