I've seen some sites that allow you to view screenshots in an interesting way:
When you click to go ahead and view screenshots, everything becomes slightly darkened and a loading symbol appears (I'm using Safari, and I see the Safari loading symbol) while the screenshot window loads. Once it loads, a screenshot appears in front of the slightly darkened layer that contains everything else. This feels a lot like Expose on the Mac.
How would one accomplish this with AJAX (and CSS, I guess)? I know nothing about AJAX, so I'm completely clueless. How would you do it without the darkened background? Does the loading symbol appear automatically, or is that a nifty graphic that people add?