The last time I had this happen to me was two weeks ago and I still haven't completely figured it out just yet. With that said, here's what I did and maybe it will work out for you. There might be a better, more complete and less destructive way to do this but this doesn't happen very frequently for me to test.
It's a two step process.
First, get Firefox to forget about the site, everything. You can do this by going to your history, right click on a link to a page on the domain you want to forget, and select Forget About This Site
. After you do this, close Firefox.
Now you want to kill any traces of the old page from Windows' DNS cache. Go to the command prompt (Win + R, cmd
) and enter the command ipconfig /flushdns
. After this close it as we're done.
The next time you start up Firefox and visit that site, it should now (hopefully) be the most recent version and not a cached copy.
ipconfig
/ifconfig
(or whatever GUI settings utility you have) to obtain the IP address(es) that your network interface is currently assigned from your network interface directly without all of the extra layers and additional mechanisms — and, as you are experiencing, scope for introducing all kinds of extra problems — interposed by using a WWW browser as a diagnostic tool.