Minimum:
<META HTTP-EQUIV="pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
<meta http-equiv="cache-control" content="no-cache">
Und dann gibt's noch den $%@#!% Internet Explorer:
http://support.microsoft.com/support.../Q222/0/64.ASP
"HTML's a cheap whore. Treating her with respect is possible, and even preferable, because once upon a time she was a beautiful and virginal format, but you shouldn't expect too much of her at this point." (Mark 'Kamikaze' Hughes)