*   The site could be temporarily unavailable or too busy. Try again in a few moments.
   *   If you are unable to load any pages, check your computer's network connection.
   *   If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

Summary: * FF failed to load due to the nonstandard port (888) * IE and Chrome works * I tried about:config -> network.security.ports.banned.override -> add 888. But doesn't work still More detail: If I go to a site with different/non standard port, eg: http://intranet:888/, it will fail. However I can use IE and Chrome for it. The error message in FF: Unable to connect Firefox can't establish a connection to the server at intranet:888. * The site could be temporarily unavailable or too busy. Try again in a few moments. * If you are unable to load any pages, check your computer's network connection. * If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.