The patent, filed in September of 2010 and published on March 15, 2012 specifically relates to the Aero Snap feature in IE9, which enables side-by-side reading of web pages in different browser windows.
The patent claims rights to pulling a tab from an existing tab bar and displaying the content of the active web page in a new browser instance when dragged to an area outside the previous browser window. It will be difficult for Microsoft to claim such rights, however, based on prior art claims that can be made by other browser makers. Additional claims that may problematic are the features to drag a tab within the same band to a different location as well as to a tab band in another browser instance.
Of course, the true patented feature is Aero Snap to enable viewing of web pages next to each other. However, some of the total 20 claims made by Microsoft are rather general and may not be enforceable, if this patent application is granted.