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If you can't connect to a website, you may see the Server Not Found error message. Learn how to troubleshoot and fix this error.

If you have a problem connecting to a website, you may see error messages like '''Server Not Found'''. This article describes how to troubleshoot problems that cause this error. *For troubleshooting other error messages, see [[Error loading web sites|Error loading websites]]. __TOC__ = Try another browser = To begin, try opening a website in another browser (such as {for win}Internet Explorer{/for}{for mac}Safari{/for}{for linux}Epiphany or Chromium{/for}). * If all other browsers cannot load the website, move on to the [[#w_no-browsers-can-load-websites|No browsers can load websites]] section. * If the other browsers can load the website, skip ahead to the [[#w_firefox-cannot-load-websites-but-other-browsers-can|Firefox cannot load websites but other browsers can]] section. = No browsers can load websites = If neither Firefox nor your other browser can load websites, your problem is not in Firefox, so you should seek help elsewhere{for linux}.{/for}{for mac}, for example, at [http://www.apple.com/support/ Apple support]:{/for}{for win}, for example, at Microsoft.com:{/for} {for mac} *'''(OS X 10.8 Mountain Lion)''': See [https://support.apple.com/kb/PH10668 If you can't connect to the Internet] * '''(OS X 10.9 Mavericks)''': See [https://support.apple.com/kb/PH14107 Solve problems with connecting to the Internet] *'''(OS X 10.10 Yosemite)''': See [https://support.apple.com/kb/PH18488 Solve problems connecting to the Internet] *'''(OS X 10.11 El Capitan)''': See [https://support.apple.com/kb/PH21608 Solve problems connecting to the Internet] {/for} {for win} * '''(Windows 10)''': See [http://windows.microsoft.com/en-us/windows-10/getstarted-why-cant-i-get-connected Why can't I get online?] *'''(Windows 8)''': See [http://windows.microsoft.com/en-us/windows/cant-connect-internet#1TC=windows-8 Why can't I connect to the Internet?] * '''(Windows 7)''': See [http://windows.microsoft.com/en-us/windows/cant-connect-internet#1TC=windows-7 Why can't I connect to the Internet?] * '''(Windows Vista)''': See [http://windows.microsoft.com/en-us/windows-vista/Troubleshoot-Internet-connection-problems Troubleshoot Internet connection problems] * '''(Windows XP)''': See [https://support.microsoft.com/en-us/kb/308007 How to troubleshoot home networking in Windows XP] {/for} {for win,mac}You should also check the following:{/for}{for linux}You should begin by checking the following:{/for} * Make sure your modem and/or router are both on and are not indicating errors. * If you are using a wireless connection, make sure that you are connected to the right access point. * Make sure your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) is not blocking connections to the Internet. For instructions on how to configure these programs, see the [[Firewalls]] article. * If you use a proxy server, make sure that the proxy server can connect to the Internet. For instructions on configuring proxy settings in Firefox, see [[#w_firefox-connection-settings|Firefox connection settings]] below. = Firefox cannot load websites but other browsers can = If Firefox cannot load websites, but your other browser can, follow the instructions below. == 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 these 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: # [[T:optionspreferences]] # Select the {menu Advanced} panel. # Select the '''Network''' tab. # In the Connection section, click {button Settings...}. # 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{for win} (such as Internet Explorer - see [http://windows.microsoft.com/en-US/windows7/Change-proxy-server-settings-in-Internet-Explorer Microsoft's guide to proxy settings]){/for}{for mac} (such as Safari - see [http://docs.info.apple.com/article.html?path=Safari/5.0/en/9299.html Apple's guide to proxy settings]){/for}. # Click {button OK} to close the Connection Settings window. # [[T:closeOptionsPreferences]] == DNS Prefetching == [https://developer.mozilla.org/En/Controlling_DNS_prefetching DNS Prefetching] is a technique Firefox uses to speed up loading new websites. To disable DNS Prefetching: # [[T:aboutconfig]] # [[T:contextmenu]] in the list of preferences, select {menu New}, and then select {menu Boolean}. # In the '''Enter the preference name''' window, enter {pref network.dns.disablePrefetch} and click {button OK}. # Select {pref true} when prompted to set the value and click {button OK}. == IPv6 == Firefox supports [http://en.wikipedia.org/wiki/IPv6 IPv6] by default, which may cause connection problems on certain systems. To disable IPv6 in Firefox: # [[T:aboutconfig]] # In the '''{for not fx11}Filter{/for}{for fx11}Search{/for}''' field, type {pref network.dns.disableIPv6} # In the list of preferences, double-click {pref network.dns.disableIPv6} to change its value from {pref false} to '''{pref true}'''. = Firefox cannot load certain websites = If you find that Firefox can load some websites but not others, {for win}first{/for} clear your Firefox cookies and cache: [[T:clearCookiesCache]] {for win} == 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 [http://en.wikipedia.org/wiki/Malware 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, see [[Is my Firefox problem a result of malware#w_how-do-i-get-rid-of-malware|How do I get rid of malware?]]. {/for} <!-- MZ credit --> <br/> <br/> '''''Based on information from [http://kb.mozillazine.org/Error_loading_websites Error loading websites (mozillaZine KB)]'''''