Have to refresh page with each return visit to get current posts and comments

I’m having trouble with returning users not seeing posts and comments made since their earlier visit to the site. If I go to a category page with comments, or the comments RSS page … and if I had visited those pages with the same web browser before (even a day before) … I get the page as it was on my previous visit and will only see the new comments/posts if I refresh the page in my browser (IE7). Users who don’t know to refresh return to the site and don’t think they have any new posts or comments, when in fact there are new ones there which become visible upon refreshing the page.

Is there a plug-in or a setting to fix this?