How do I stop Firefox screensaver which I cannot cancel?

Your question reminds me of this earlier thread: [https://support.mozilla.org/en-US/questions/971892 I want to delete all firefox screen savers]. In that case, the problem was an add-on named Wallpaper Rotator. Could you check for that? Visit the Add-ons page using either: * Ctrl+Shift+a * orange Firefox button (or Tools menu) > Add-ons In the left column, click Extensions. Then check out what you have. There may be some surprises here. If you don't recognize something, you can disable it. If you're sure you don't want it, you usually can remove it. ''If the Remove button is missing, then try the Windows Control Panel, Uninstall a Program.'' Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Does that fix it?