Problem targeting frame/image in Netscape 7.2

I’m using the following onMouseDown attribute to swap a header image in a parent frame (“head”), but it’s not working in Netscape 7.2 on Mac OS X. Can someone have a look and tell me what’s wrong, or recommend a better solutions?

<a href="mgnav_galleri.htm"

It’s up at if you want to have a look.

The index is made up of 3 iframes. “head” contains what you see. The nav next to the logo is in it’s own iframe, “mgnav” (within “head”). The header image I want to change is in the “head” iframe.

Really appreciate any help.