Why does my image wiggle on hover?

Question

Can anyone help me understand why the videos image (but not the play icons) at http://www.alternativeradio.org/pages/free-downloads wiggle up a pixel then down a pixel when I mouseover, then again when I mouseout? The effect is slower on Firefox, so it probably has something to do with CSS transitions.

Answer 1

Was having the same issue with an image gallery using CSS filters and transitions. Got rid of the unwanted wiggle through help from this answer.