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.