'The page you requested was not found' after finish to invite users on facebook application

Question

Hi,

I tried create a invitation function on iFrame facebook application, but i have errors when submit it, so when user done invite a person, then it should redirect to action url that we set, but the page is not go to the right url, it says "The page you requested was not found."

here is my code that i use :

<fb:serverFbml>
     <script type="text/fbml">
        <fb:fbml>
            <fb:request-form
                action="http://mydomain.com/action"
                method="GET"
                invite="true"
                type="XFBML"
                content="This is a test invitation from XFBML test app" >
                <fb:multi-friend-selector
                    showborder="false"
                    actiontext="Invite your friends to use Facebook." />
             </fb:request-form>
         </fb:fbml>
    </script> </fb:serverFbml>

Thanks