EDIT: I see that you have another thread about this with more information, so I'm going to lock this thread. Please continue here: *[[/questions/978442]] ------ When do you see this message? If it happens with visiting a web page then this is a problem that the owner of this website needs to fix and you can't do anything about this normally. ----- Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files. *Hold down the Shift key and left-click the Reload button *Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux) *Press "Command + Shift + R" (Mac) Clear the cache and cookies only from websites that cause problems. "Clear the Cache": *Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now" "Remove Cookies" from sites causing problems: *Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"