I call mine p.gif. I still use one today, because, in order to maintain the Any Browser promise, I use an XHR request for pre-XHR browsers, which just sets the

I call mine p.gif. I still use one today, because, in order to maintain the Any Browser promise, I use an XHR request for pre-XHR browsers, which just sets the src of the spacer gif. If any return values are needed, they're populated into the src attribute with a redirect. :)