This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
If you want to know the URL of the page from which the request was sent, you can try reading the HTTP-REFERER header. By the way, are you trying to implement some security feature using this information? If not, why do you need this info for?