I guess that you have implemented a .net ascx.
Solution 1: Don't redirect to another page. Set the textboxes and the button unvisible (or better the pane where they are placed on) and show another pane with "Thank you".
Solution 2: use a real redirect (Response.Redirect(URL))
By the way: the target where the post goes is defined in the form-tag, not in the submit-button. So the simple submitbutton only does a Post-Back.
hth, Thomas
• 2007/2008 MVP •
www.thoehler.com • Bad Homburg, Germany