Load function changes page layout!?

Load function changes page layout!?

I'm fairly new to Jquery, and I'm using the load function to inject a page into my layout. It works fine, however after it loads the page the layout changes dramatically and eliminates pretty much all of the CSS in the HTML file.

The page im loading is a PHP page, could that be why? Is there something I have to insert into the PHP file to stop the display from changing upon loading?

Thanks!