Disable animation on images with mouse hover

Afternoon,

On my site that I am overhauling, I noticed recently that the images that I have on pages are starting to bounce up when hovering the mouse over it. It seems to leave my header images alone, but the rest are all over the place.

As an example, I have created a portal for one of the games my community supports, and all the images on the page serve as links for all the sub portals. But when trying to select one, an animation will occur and can be annoying for some users to select.

Portal: http://epeengaming.com/smash/

I don’t know what I have to disable so this isn’t a normal function, or what css script I have to enter for each image so the images don’t do anything on hover. I only noticed this happening after updating the theme from two past revisions.

Any suggestions?

Cheers,
MK