how to implement url masking

Question

I want to implement Url masking. for example .
 
I have one website www.abc.com/Login.aspx when user enter this URL in browser he will be redirected to www.xyz.com/Login.aspx.
 
But i want to show user the previous URL i.e. www.abc.com in the browser.
 
I have many URL like abc.com for which user will be redirected to xyz.com ,i want to know from which URL was Redirected to xyz.com
 
and also how to hide URL of xyz.com
 
Thanks in advance.