The biggest problem in web pages, particularly ASP.NET forms, is that it can take up a long time to process once it is submitted. This can be a problem specially when submitting forms. The user thinks that your site is not submitting their input so they press the submit button again hoping to get the information faster. One way we can solve this is by disabling the submit button once it is pushed, but what if your page has more than one button?
In this article, we’ll show you how to disable all your ASP.NET form controls during a postback and show a friendly animated GIF while the page is posting back.
Read the rest of the article here: http://www.codeproject.com/Articles/35061/Lock-ASP-NET-Page-and-Show-Animated-Image-While-Wa