I want to do something similar to what Chris did on this site when you click "submit" after creating or replying to a topic. It says that your message has been posted, and it redirects you back to the post you commented on.

I have a form, and when someone fills it out, I would like it to send them to a page that says "your message has been sent" and then redirect them back to the previous page.

How would I go about doing something like this?