How do i auto fit my WP blog to smaller screen sizes?

Hi I have a test site up at the moment with a very large banner. It takes most of the screen on a 15.6″ laptop where as you see what’s beneath it on a 22″ screen.

I wondered if there’s a plugin for resizing the screen to auto fit smaller screens so those users can see the whole of the page on their display??

I did see something that did this that would resize WP blogs for hand held’s like iphone but can’t remember what it was or whether it would work for smaller laptop screens???