The new version of Gmail included major performance improvements and new features such as colored labels, group chat and rich emoticons, invisible mode, AIM integration, Gmail Labs, an updated contact manager, and remote sign out. But as these features are very complex only newer browsers could handle them.

The Gmail team has written a new code with small simplifications of user interface which will work in Internet Explorer 6 if you update IE6 with the specific patch that was released by the IE Team performance problem with how the script engine allocates and frees memory.

This a good move as (still) majority of people use Internet Explorer 6 as there default browser and Gmail was not available to them.

[via The Official Google Blog]

[UPDATE] There seem to be lot of confusion here. Version 2.0 of Gmail was provided to the users of Firefox 2 and Internet Explorer 7 months back but was not available to the users of  Internet Explorer 6 because IE 6 wasn’t powerful enough to handle the features of Gmail 2.0. The gmail team wanted Gmail 2.0 to reach to everyone but that is not possible until it is made available to Internet Explorer 6 users….and that’s what they did now. (I hope this cleares all the confusion)

THANK YOU

-vinit