My app loads one of several dynamically generated reports, implemented as user Controls, (*.ascx files) into an Update Panel.  I am trying to do this without a page postback.  However, client side code needs to validate several things before issuing the asynchronous request.  In IE, I was using an ASP.Net custom Validator control hooked to a client side script
(GenerateReport(sender, e)  {...}  
to control this, (using e.valid = true/false; to control whether the asynchronous request to update the content in the UpdatePanel was sent or not, but I have discovered that Firefox does not implement ASP.Net Validators properly.

So now I am trying to accomplish the same functionality simply using a client side script that calls __doPostBack(eventTarget, eventArgs); 
But I can't seem to get the __doPostBack to call the Microsoft AJAX asynhcronous call, instead of doing a complete page postback.

How do I do that?  Or  is there a better way to do this. 

Another option I have considered is to put the user control into a web service, that somehow just returns the innerHTML of the user5 control rendering process, but I can;t seem to figure that out either..

ideas anyone?

I've been fighting the same problem the last couple of days.  Here is what I just finally came up with...

 I write the __doPostBack on the server side and insert it into an onClick event on a control.

e.Row.Attributes.Add("onClick", sOnClick); //  I'm adding this to a gridview, I'm guessing this will work elsewhere too.

Then in the Page_Load I parse the event arguments and call the appropriate function

G

You can use __doPostBack() to refresh an UpdatePanel, if you target the UpdatePanel itself.