[Hall of Famer]

umm you can create a table in your database that behaves somewhat similar to the prefix_voters. Whenever a user visits this page, a row is automatically inserted into this table recording his/her userid, username and date of visit. Then write your script to check if the current date is the same as the date stored in your table. If so, the user has apparently visited the page for more than once in a day. All you can do next is to generate an error message for the specific user should this happen.