Simple image rollover problem

Hi,

I have inserted rollover images in Dreamweaver CS4. They all work, except they don’t remain in the downstate when on the relevant page. I would really like this as I feel it’s important to give feedback.

You can see my page here:
http://zroam.com-tellmemore.info/Index.php

As you can see, ‘home’ should be in the downstate, but is not.

I know this is simple, but I can’t seem to find the right words to search for this.

Thank you.