This is a peculiarity of Microsoft Internet Explorer (or at least some versions of it) and possibly other browsers.
When a link is invoked with the shift key held down, MSIE opens the requested link AND a blank window. This happens independently of Friday.
There's little Friday can do to prevent this. If you release the shift key quickly, it shouldn't happen, however.
Naturally, all content & site maintenance by
Friday The Automatic FAQ Maker