If you're trying to do what we did with one of our projects...re-write the url...for example the users types in www.page1.com
and we want to rewrite that url to www.page2.com
. Not a simple redirect.
Then it cannot be done from within web.config...it has to be at the IIS level. You will need to create an ISAPI filter.
Again, if you are trying to re-write their url. If so I can point you in the write direction on how we did it.