I just came across some new tweaks to the web interface of Twitter – not sure how long they have been there but…
Here is what the box looks like on initial hover. Click on the more link then you will see the expanded box:
This contains everything you would see in the user bio area on their main Twitter page.
If the user is not yourself then you will also see the icon for a drop down menu that used to appear on the right hand side of the tweet. Of course clicking on it reveals the drop down menu:
These are very nice tweaks as it keeps you on your timeline page and allows you to see info that is normally only at a users twitter page. Very helpful for screening who your seeing tweets from.