On every page (sitting in the master) I have the login fields.
In the other pages I have different controls, e.g. a contact formular.
How can I set more than
There is a way to switch forms by using a custom HtmlForm class that can have the form tag rendering toggled on and off. I put out a blog post on how to use this for PayPal and get around the ASP.NET single form tag problem:
http://www.codersbarn.com/post/2008/03/08/Solution-to-ASPNET-Form-PayPal-Problem.aspx
Hope this helps :-)