How do you the change backround of only one specific page?

I have different portals but I only want one of them to have a specific different backround. How do I do that? With Css cheet? Templates? If so whats the code to change the backround?

I don't think it can be done as that would require the muti Theme option.

With portals you mean widgets on the portal?
That is possible when you have PunBB or PhpBB2 through templates but you can only do that to a few