For example, if I go to www.yahoo.com/thispage, and yahoo has set up a filter to redirect /thispage to /thatpage. So whenever someone goes to /thispage, they will land on /thatpage.
If I use httplib/requests/urllib, will it know that there was a redirection? What error pages?
Some sites redirect user to /errorpage whenever the page cannot be found.
With requests, you get a listing of any redirects in the .history attribute of the response object. It returns a Python list. See the documentation for more.