Start Firefox in safe mode (Close firefox, press SHIFT key on the keyboard, and click on the firefox icon to launch it again, keeping the shift pressed. A small popup will ask you if you want to start in safe mode or reset firefox, choose the option to start in safe mode).
Open the page that refreshes automatically.
Use the computer normally for a while (play your games)
Check firefox, does the page reload even in safe mode?
If it doesn't, you have an add-on that's causing pages to auto-refresh.
If it does, well, some pages are designed to auto-refresh so that you see the latest content all the time. It's not a problem, it's a design decision. It can be stopped by disabling javascript, but disabling javascript might (and probably will) make many many many pages fail to display correctly.