Possible Duplicate:
How does the User Card popup work?
The avatars (from Gravatar) used in the Stack Exchange sites, specifically Stack Overflow, now have an embossed effect. Am I right?
Was this just added recently, or is it a feature from Gravatar?
It's a new feature for indicating the pop-up user cards that are available for users with at least 1k reputation and that have added profile information. Hover your mouse over any user icon with the shadow to see the effect.
For more information see the new blog post Expanding User Cards
