is it possible to redirect an URL http://www.siteA.com to http://www.site2.com/Default.aspx?SiteSource=siteA without changing the browser’s URL?
Similarly, accessing http://www.siteA.com/Page2.aspx will redirect to the http://www.site2.com/Page2.aspx?SiteSource=siteA
You can also use mod_proxy (or similar functionality for a different web server) so that the page your server serves is the same as the remote page. But this has some security and performance implications (you’re letting the client make your server do arbitrary work copying data across the network from the remote server).