If you look at the source of the page
http://www.xsiteproforums.co.uk/regi...o=requestemail after coming from the welcome headers link you will see that the hidden field is being set to <input type="hidden" name="url" value="http%3A%2F%2Fwww.xsiteproforums.co.uk%2Find ex.php" />. For some reason vbulletin is encoding the url but then trying to load the encoded url afterwords. Welcome headers don't have anything to do with the source of this routine... rather vbulletin pulls the referring page from the user directly. I will see if a vb developer can't help explain the process.