how can I implement a feature on the server side where after a user clicks submit for the first time, clicking submit again will bring the user to a page showing "Please wait X seconds to submit". I've seen this feature on several sites but can't resources on it.
When the user clicks submit, store the current time in the user's session. The next time they click submit, compare the current time to the time last stored in the session. If the difference is less than X seconds, redirect to the page which tells them to wait.