Occasionally, someone requests that one or more web pages be removed from the Internet. This is usually a class web page that lists the answers to a quiz from last quarter, and the instructor wants to re-use the same quiz this quarter and doesn't want the students to be able to find the answers on-line.
The short answer is: you can't.
The long answer is as follows:
The Internet has several very prominent services (like Google and the Wayback Machine) that cache web pages, often for very long periods of time - in the case of the Wayback machine, forever. Once these services cache our web pages, it is basically impossible to remove the cached information from them. It is certainly more work to remove the web pages from these caches than it is to create a new quiz.
Some instructors, upon hearing about such services, reply that they didn't know about the services and therefore their students don't either. That's almost certainly incorrect. Students at the university level have grown up with the Internet almost their whole lives and are well aware of the availabilty of caching services.