Safari Back Button goes to old cached page, os X El Capitan, iMac On certain websites I visit Safari has a consistent problem.  Using the back button brings up an old cached version of the page.  Refresh works fine.  An example is http://forum.porsche356registry.org/viewforum.php?f=1.  If I read the threads on that page and click back, it will eventually start bringing up an old cached view of the page without refreshing the list of threads.

I enabled the Develop menu in Safari and watched what happened in the inspector's network tab, when clicking back vs. clicking refresh (of the same page).  They do different things.  Refresh always runs the script viewforum.php, which I assume refreshes the list of topics.  Clicking back often did not run that script.  Looking for an explanation...
I think the explanation is that Safari often uses the cached version of the page when you use the back button. If you want to force a refresh, you hit refresh. If you are on a forum and want to go back to the thread listing, you can usually click on a "breadcrumb" link near the page header. That will have the same effect as using the back button and hitting refresh, because Safari will understand your click to signal a new page visit.