[plug] HTTP return header?

[J Michael Gilks]

I am writing a site for Mater Dei College and on the login page I need to 
validate entries on the form before submitting it to the database. Using the 
onSubmit method of the form I check entries and if they are missing setfocus 
to that entry then return false. This should stop the submit process, but it 
doesn't. I get my error message box come up and then the form submits anyway.
What I would like to do is include a header on the action page to redirect 
back to the login page, with the information intact, if this error occurs.
I am using Quanta as an IDE, with PHP scripting on an Apache server.
I am sure there is an appropriate header as every browser has a back button 
which works. I just can't find a reference.
Can anyone help please.
Love
Mike.