So the style designer says "thou shalt use an image button", but the button is going "oh no thou shaln't".  The problem is, the button works fine as long as all validators on the page are valid, but if any required fields are empty or anything of that sort, clicking the button activates all the validators and DOES NOT CALL its onclick event handler.  This might be appropriate if the button were for submitting the page, but it's not -- it's a side popup, which needs to work independently of whether the page is submittable.

I've tried setting CausesValidation false, and AutoSubmit false, but the behavior doesn't change.  How can I tell the button to just be a button, and not try to set itself up as a guardian of morals for the rest of the page?