twitter/bootstrap — pull request #1765 by biojazzard (2012-02-06 13:50:00+00:00)
Title: Added box model: "box-sizing: border-box;"  to thumbnail class

This workarround lets you put images at 100% width without overflowing the grid with:
.-the 4px padding plus
.-the 1px border.

Now works everywhere except IE7 and older.
http://caniuse.com/css3-boxsizing