Change Unity Player Not Installed background

Allot of people who visit our site come from Corporate environments where they are restricted on the plugins that they can install. Because of this they can't always run unity in their browser.

What i would like to do, is if my webpage detects that the user doesn't have unity installed, the section in the div class="missing" tag, i could overwrite with my own code. Something other than just the install unity plugin image and link. This way i could ask them to install the unity plugin or download the standalone version of our software.

Currently if i put anything in the div class="missing" tag in my html document it gets overwritten by unity code, displaying the standard install unity. Any one have any thoughts on how i can do this?

Thanks for your help, C