On a feature by feature comparison, Firefox either matches or surpasses IE.
  Internet Explorer 6 (with XP SP2) Firefox 1.0
CNET rating 7.0 8.0
Pop-up blocker Yes Yes
Able to selectively block pop-ups or view blocked pop-ups later Yes Yes
Built-in RSS reader No Yes
Able to view multiple pages within same window using a tabbed structure No Yes
Third-party plug-ins Yes - many Yes - some, but more everyday
there are thousands working on this, not just one greedy corp
PNG, alpha transparency support No Yes
Uses ActiveX technology Yes No
but proprietary technologies only benifit one - M$
User interface skins No Yes
OS compatibility Windows XP SP2 and later only* All versions of Windows,
Mac OS X,
and several Linux distributions
Adherence to web standards set by society No Yes
* Going forward, Microsoft will upgrade only the versions of Internet Explorer running on Windows XP SP2. The last standalone version of Internet Explorer 6 will work on versions of Windows up through Windows XP SP1.
Because this is their way of insuring that you move to their new code that allows them better control over your PC.