So I built a little piece of php to make a nice automatically generating pagination for my results pages and want to add a way for the user to change how many are shown per page.. but got a question for the usability gurus here
I am thinking about retaining the results count so I can set the beginning result correctly.. In example.. lets say a user views 10 per page and looks through three pages of results and then decides to change the per page to 20, should I
A. Start the results back to the beginning of the results showing the new number per page
B. Send them to a new page showing results 31 - 50, basically reloading the page they are on with the new preference.
C. Send them to a new page showing them results 41 - 60. setting the new preference as they move off the current result set.
Is it common practice to take what has been seen into consideration when changing the number the user wants to see at one time?