Your cat may have switched on caret browsing. *http://kb.mozillazine.org/accessibility.browsewithcaret You can press F7 (Mac: fn + F7) to toggle caret browsing on/off. *Tools > Options > Advanced > General > Accessibility: [ ] "Always use the cursor keys to navigate within pages" *http://kb.mozillazine.org/Scrolling_with_arrow_keys_no_longer_works *http://kb.mozillazine.org/Accessibility_features_of_Firefox ----- It is possible that your security software (firewall, anti-virus) blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program. Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process. See: *https://support.mozilla.org/kb/Server+not+found *https://support.mozilla.org/kb/Firewalls *https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating