Shoutbox

Yea thats what i thought also but most people who view my site are not firefox users as they are not regular computer users more like the 'check email use msn' people. so therefore the majority use IE.
I know you can combat the problem by clearing your cache but the problem is not on my computer its theirs. so i cant go and either explain to them or do it myself to everyone elses computers.
Is there a way to tell the browser as the page loads to load as new from the host rather than use cache??