Can I create an ASP.NET ImageButton that doesn’t postback?

I’m trying to use the ImageButton control for client-side script execution only. I can specify the client-side script to execute using the OnClientClick property, but how do I stop it from trying to post every time the user clicks it? There is no reason to post when this button is clicked. I’ve set CausesValidation to False, but this doesn’t stop it from posting.

Force ASP.NET to generate JavaScript for all User Agents

I noticed recently in my ASP.NET web application that if I set my User Agent to an empty string (using a FireFox plug-in to spoof the user agent), then ASP.NET will not generate the javascript required to perform postbacks. More specifically, if you try calling the __doPostBack(a, b) function from your javascript, you will get an error saying that function is undefined.