As we all know the HttpApplication object holds objects regarding the requested page (HttpRequest) and the page where we are supposed to be redirected (HttpResponse); I need to get the url of the page which requested the page; how could I get it from the HttpApplication ?
You want to check the url referrer header like so:
string MyReferrer = Request.UrlReferrer.ToString();
This value is set by the browser however - so can't exactly be trusted from a security viewpoint.