How to reach the Root Directory in ASP.Net 2.0?

If I have a site with a page address like:





www.somthing.com/thisapplication/thisp...





how can I set up my loginUrl in the forms auth section of web.config to go back to the root directory?





To a page address like:





www.somthing.com/thispage.aspx





I can't get ~/thispage.aspx to work in the web.config.

How to reach the Root Directory in ASP.Net 2.0?
how about ../thispage.aspx