There's no rule that says that browsers have to pay attention to your 'no-cache' instructions so you might want to add the following:
<meta http-equiv="Date" content="-1">
<meta http-equiv="Expires" content="-1">
Note: HTTP headers do not support relative dates, but any illegal date is taken to have occured sometime in the past.
“The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.”
—Tim Berners-Lee, W3C Director and inventor of the World Wide Web