The bar is an overlay that Meebo offers to website publishers that readers can use for instant messaging and other social activities. Now website owners can push notifications to readers regardless of where they are on the site.
The notifications pop up out of the bar just like in the picture we've included. They can be whatever the publisher wants them to be. The most obvious usage is to notify a reader of just-breaking news that they might not see if they're not browsing the front page, but there are many other possibilities.
Meebo struck a deal with AdWeek, which will start using notifications immediately. That will give folks a way to see the bar in action when they're thinking about whether or not they'd like to add it to their own sites.