Clear Form onLoad

Hello everyone. I have been teaching myself PHP over the past few months. I have to say that I am impressed with the learning curve for it. I do have a problem that has popped up that maybe someone could help with. I have a javascript that clears my forms using the onLoad command for my other sites. I recently started a php site. however my script is not working. Is there a way to make my script work with onLoad? If not is there a way to clear the form when the page loads? I dont want people to be able to click the back button and resubmit the same information a second time. Any help would be greatly appreciated Bill