Official Gmail Blog: New Gmail code base now for IE6 too: "Over the last few months, we've been working with the IE engineers at Microsoft to address these issues: they released a critical update to their JavaScript implementation that fixed a performance problem with how the script engine allocates and frees memory. We also made small simplifications to the UI when it runs in IE6 to improve stability. For example, we removed the drop shadow from contact pop-ups and the rounded corners from chat moles, both of which tended to cause problems in IE6."