According to the Official GMail Blog there are changes a foot over at Gmail.

recently the Gmail team has been working on a structural code change that we’ll be rolling out to Firefox 2 and IE 7 users over the coming weeks (with other browsers to follow). You won’t notice too many differences to start with, but we’re using a new model that enables us to iterate faster and share components (we now use the same rich text editor as Groups and Page Creator, and the Contact Manager can be seen in several Google apps). A few other things you will notice are some new keyboard shortcuts and the ability to bookmark specific messages and email searches. more