Mozilla Firefox Help

  This article describes problems where Firefox cannot load websites but other Web browsers (such as   Internet Explorer ) can. When this happens, Firefox may show a   Server not found   or   Unable to connect   error message.  Fix Firefox Error For other error messages that display when you try to view websites in Firefox, see Websites don't load - troubleshoot and fix error messages. If none of the Web browsers on your computer can load websites, see Firefox and other browsers can't load websites.    Internet Security software blocking Firefox If you were able to load websites until you updated Firefox or until your Internet security software was updated, reconfigured or a new one was added, your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) is likely preventing Firefox from connecting to the Internet. In general, you should make sure your Internet security software is up-to-...

  A  user agent  tells websites what type of browser and operating system you're using. This information helps the web server deliver content that's compatible with your browser. If websites tell you that your browser is outdated or incompatible even though Firefox is up to date, an incorrect user agent may be the cause. This article explains how to fix problems with your Firefox user agent so that websites work properly.  Fix Firefox Error User agent issues You can change Firefox's user agent to trick websites into thinking that you're using a different browser or operating system. Web developers might do this to see how their websites will appear on different systems and browsers. Sometimes, add-ons and other installations can change your user agent without your knowledge. Websites may not display correctly or may show a message that your browser is outdated or incompatible, based on the detected user agent. It's important to switch Firefox back to the  defaul...