This article describes why Firefox would not be able to access any web site even when other programs (like Internet Explorer) can. For situations where all programs are having problems or where Firefox can load some websites but not others, see Error loading web sites.

Table Of Contents

• Security software
• Panda Anti-Virus
• Connection settings
• Connection settings not remembered
• Firefox is in offline mode
• IPv6

Security software

Internet security software, including antivirus programs, antispyware programs, and especially firewalls can block Firefox from accessing the Internet. This is especially common after a Firefox upgrade. When security software blocks Firefox, Firefox may give one the following errors:

• Unable to connect
• Server not found

In most cases, you can reset your software's permissions for Firefox and Firefox will be able to connect again. For specific instructions on how to re-configure various security programs to allow Firefox, see the Firewalls article.

Note: In some cases, disabling an Internet security program or firewall does not stop all of its parts from being active. A program that reports that it is disabled may still be able to block Firefox.

Panda Anti-Virus

Older versions of Panda Anti-virus can cause connection problems.

Note: Information on this issue is no longer available on the Pandasoft Web site. You should upgrade your version of the software, disable it, or replace it with a different anti-virus program.

Connection settings

While Firefox will work out of the box for most users, some users will have to configure Firefox for it to be able to access the Internet. Firefox may give one of the following errors when it's not properly configured:

• The proxy server is refusing connections
• Server not found

Verify that your connection settings in Firefox are correct. You can use the settings of a program that works as a reference. For example, if Internet Explorer works, open Internet Explorer's dialog to see the correct settings for your computer.

1. Open Internet Explorer.
2. In the Tools menu, select Internet Options.
3. Click the Connections tab.
4. Click LAN settings.

Then, compare the settings to those in Firefox.

1. At the top of the Firefox windowOn the menu bar, click on the ToolsFirefoxEdit menu, and select Options...Preferences....
2. The OptionsPreferences window will open. In the Advanced panel, click the Network tab. To review your Firefox connection settings, click Settings....
3. Make any changes to your Firefox settings to match those you found in your working installation of Internet Explorer.

After reconfiguring Firefox, close it and re-open it and try to access a web site.

Connection settings not remembered

If you're still having problems, check the connections settings again. If you notice that your changes haven't been remembered, you may have some software on your computer that is overriding your settings.

One program known to override connection settings is Hide IP. To remove the override:

1. Open the profile folder.
2. Open the user.js file for editing.
   • If there is no user.js file, you don't have any overriding settings, so this isn't your problem.
3. Remove any lines that have the word "proxy" in them.
4. Save the file.
5. Restart Firefox and try to change your settings again.

Firefox is in offline mode

Firefox has an offline mode where it won't try to use the Internet. If your Firefox is in offline mode, it will show Offline mode when you try to use web sites. To turn off offline mode:

1. Open the File menu.
2. If there is a check mark beside Work Offline, click Work Offline to remove the check mark.
   • If there's no check mark, Firefox is not in offline mode.

IPv6

Internet Protocol version 6 (IPv6) can cause connection problems on some Internet connections. Firefox uses IPv6 by default. Disable IPv6 to see if this solves your connection issues:

1. In the Location bar, type about:config, and press EnterReturn.
   • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
2. In the displayed list, type network.dns.disableIPv6 in the Filter textbox.
3. Find the entry for network.dns.disableIPv6.
4. If the value is false, double-click on it, to change the value to true.
   • If the value is already true, IPv6 is already disabled, so it isn't causing your problem.
5. Close Firefox, start it again, and try to reach a web site.

If disabling IPv6 doesn't resolve the problem, re-enable IPv6 by setting the preference back to false.

Based on information from Error loading websites (mozillaZine KB)