How independent is it of other activity in Firefox or on your system? Can you find any of these patterns: * Appears when visiting particular websites * Appears when loading the home page (using Ctrl+n or Home button) * Appears when opening a new tab (using Ctrl+t or "+" button) * Only appears when using Firefox desktop shortcut * Appears at particular times of day (often even if Firefox is fully closed) * Appears when taking other actions on the computer (e.g., using a freeware program) ---- Your Firefox settings look reasonable, so I don't see an obvious culprit. I suggest starting your investigation and cleanup here: (1) Open the Windows '''Control Panel''', Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Take out as much trash as possible here. (2) Check your '''connection setting''' to make sure it hasn't been pointed to a hijacked DNS server: "3-bar" menu button (or Tools menu) > Options > Advanced > Network mini-tab > "Settings" button The default "Use system proxy settings" should piggyback on your Windows/IE "LAN" settings. You also could try "No proxy" to see whether that works better. (3) Open Firefox's '''Add-ons page''' using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click '''Plugins'''. Set nonessential and unrecognized plugins to "Never Activate". In the left column, click '''Extensions'''. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. Often 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. Any improvement? (4) You can search for remaining issues with the '''scanning/cleaning tools''' listed in our support article: [[Troubleshoot Firefox issues caused by malware]]. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.