There isn't much you can do on the server side, because there's no way to know whether the second request is legitimate. One solution we have experimented with is the disabling the submit button after it is clicked. You can do so via the onclick event:
In fact, we have just implemented this technique in the message posting window of the updated Forum software that we released today.
Sent by Justin Masse on 10/28/2004 06:45:55 AM:
Hello, does anyone have a coding technique to avoid what I call the "HangryLunatic" problem? The "hangrylunatic" is the person that clicks on a link a thousand times because he thinks that the page will open more quickly this way (of course, each times he clicks on the link, the script restart from 0). That could be something very usefull.
Of course, we would have to allow people to call multiple scripts at the same time but maybe we could refuse a second execution of the same script (with same parameters etc.)...