“Are you sure you want to send a form again”?

"To reopen this page Safari must resend a form. This might result in duplicate purchases, comments, or other actions.”

Almost every time I enter in a piece of information on a website for a search, see the results, and then try to go back, I get this pop-up notification. It is annoying as ****! I rarely encountered this with Internet Explorer.

Why does Safari do this?

And, is there a way to make Safari stop doing it?