Firefox cannot load websites but other programs can

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This article describes problems where Firefox cannot load websites, but other web browsers (such as Internet ExplorerSafariEpiphany) can. When this happens, Firefox may show a Server not found or Unable to connect error message.

Table Of Contents

Cannot load websites after updating Firefox

If you were able to load websites until you updated Firefox, your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) is likely preventing Firefox from connecting to the Internet. Some Internet security programs can block Internet access even when they are in a "disabled" state.

In general, you should remove Firefox from your program's list of trusted or recognized programs, then add it back. For instructions on how to configure some programs, see the Firewalls article.

Firefox connection settings

If you connect to the Internet through a proxy server that is having connection problems, you will not be able to load websites. To check your Firefox proxy settings:

  1. At the top of the Firefox windowOn the menu bar, click on the ToolsFirefoxEdit menu, and select Options...Preferences....
  2. Select the Advanced panel.
  3. Select the Network tab.
  4. In the Connection section, click Settings....
  5. Change your proxy settings:
    • If you don't connect to the Internet through a proxy (or don't know whether you connect through a proxy), select No Proxy.
    • If you connect to the Internet through a proxy, compare Firefox's settings to another browser's (Such as Internet Explorer. See Microsoft's guide to proxy settings)(Such as Safari. See Apple's guide to proxy settings).
  6. Close the Connection Settings window.
  7. Click OK to close the Options windowClick Close to close the Preferences windowClose the Preferences window

If you find that changes you make to your Firefox connection settings are not remembered when you restart Firefox, see Preferences are not saved.

IPv6

Firefox supports IPv6 by default, which may cause connection problems on certain systems. To disable IPv6 in Firefox:

  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 Filter field, type network.dns.disableIPv6.
  3. In the list of preferences, double-click network.dns.disableIPv6 to set its value to false.
3.5/3.6:

DNS Prefetching

Firefox attempts to speed up loading new websites by using DNS Prefetching, which can cause page load errors with some system configurations. To disable DNS Prefetching:

  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. Right-clickHold down the Ctrl key while you click in the list of preferences, select New, and then select Boolean.
  3. In the Enter the preference name window, enter network.dns.disablePrefetch and click OK.
  4. Select true when prompted to set the value and click OK.

Firefox cannot load certain websites

If you find that Firefox can load some websites but not others, first clear your Firefox cookies and cache:

3.5/3.6:
  1. At the top of the Firefox windowOn the menu bar, click Tools, then select Clear Recent History....
  2. In the Time Range to clear: drop-down, select Everything.
  3. Click the arrow next to Details to display the list of items that can be cleared.
  4. Select both Cookies and Cache.
  5. Click Clear Now.

3.0:
  1. At the top of the Firefox windowOn the menu bar, click Tools, then select Clear Private Data....
  2. Select both Cookies and Cache.
  3. Click Clear Private Data Now.

Windows:

Check for malware

If clearing your cookies and cache did not enable you to load the websites that did not work in Firefox, you should check your computer for malware. Certain types of malware are known to target Firefox and can prevent it from loading various websites:

  • If you have an antivirus or Internet security program, update its detections database and do a full scan of your system.
  • If you still have problems, you can get a second opinion by scanning your system with an online antivirus utility, such as TrendMicro Housecall or Panda ActiveScan.




Based on information from Error loading websites (mozillaZine KB)


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Page last modified on Wednesday 24 of February, 2010 05:57:23 PST.
Contributors to this page: AliceWyman , underpass , lor , Bo , Chris_Ilias and np .
- This is a support/troubleshooting article -