Image link moves on hover

I am modifying the footer of a wordpress site to include four affiliate logos and their associated homepage URLs.
Whenever the image is hovered over, the image container shrinks and moves the page below it up slightly, as well as jolting the image slightly to the left.

URL: http://giant2.cogiva.com/

each image has the following CSS in addition to the theme default:

#image-9 a {
    outline: none;
    position: relative;
}

#image-9 a img {
    outline: none;
    position: relative;
}

#image-9 img {
    border: none;
    position: relative;
}