how do i stop refresh key?!

[Anmar]

hi..

check this site please:

http://www.annajat.com/annajat/upload/

and try to refresh it two times or three you well get a message telles you that you have to wait 10sec to refresh the page!
how do i do that.. it worked in all browsers..
i realy need it badly to stop attackers from overloading the server.

thanks..
Anmar