This is a small set of enhancements based on the original subModal with ideas taken from Lightbox Gone Wild. For the bandwidth conscious submodal.js is a packed version (1/3rd the size) of submodalsource.js. To check out a demonstration, click the button or hyperlinks below. This solution uses an iframe and is currently not draggable.
This demo is known to work in IE 6.x, FireFox 1.x, Safari, and Opera 8.x (transparent shading doesn't work in Opera)