Safari cannot display Fireworks swap images

I am running OSX 10.8.2

I am using Firworks CS 6

I use Safari 6.0.1

I am using Firfox for the Mac 18.0.1

Firefox 18.0 for the PC

The url in question is http://petemccabe.com

There are two swap behavior button on the page. They are identical except the lower one displays in all the browers abod except Safari.

I the other browsers, both image swap over bars display.

Is there a javascript or a line of HTML code I can insert in the header to fix this problem?

Thanks for the help.