Ah! It may help if I provide a link to my site for which you can see the main login form page in action:www.beyarecords.com
You will notice, if viewing the source page, that first line read as:
<!DOCTYPE page PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "
If I change my sitemap so that the DOCTYPE is for html 4.0, ala html, and remove the onload command from the body tag then all is fine.
If you submit the form, as is, without filling in any details the page will reload.