you can use this meta balise
<META HTTP-EQUIV="Expires" CONTENT="Mon, 30 Jun 1999 14:30:00">
with %timestamp% you can detect the begining of time when server give web page.
by example:
<HTML>
<META HTTP-EQUIV="Expires" CONTENT=expire_date()>
<script ......>
function expire_date()
{ expire_date=%timestamp% + delay}
</script>
make test i have not testing that
