I was looking through Pingdom Tools to see how a client's site was loading when I noticed a 404 error for an image file. What caught my eye was the URL pointed to a Thesis Theme directory and I've never used Thesis. I tracked down the image to this selector in the forms.css file:
#content_box .post_box .format_text .gform_footer input.button {background:url("../../../themes/thesis_17/lib/images/submit-bg.gif") repeat scroll 0 0 transparent; border-color:#CCC #999 #999 #CCC; border-right:3px double #999; border-style:double; border-width:3px; color:#111111; background-color:#E3E3E3; cursor:pointer; font-weight:bold; overflow:visible; width:auto !important; font-family: Georgia,"Times New Roman",Times,serif; font-size:1.143em; padding:0.313em 0.25em}