Codeplex green overlay on submit

Dec 20, 2007 at 4:16 PM
When you submit a comment on some of the sites or complete some forms on the codeplex site a transparent green overlay is placed over the form and access to the form is disabled until the postback completes. I currently have a rather clunky solution to avoiding the double postback problem and this looks like a nice alternative.

Can anyone tell me how is this done? No detail needed I'm just looking to a pointer to a control or guide, or whatever there is.