server not found

User Help for Mozilla Firefox

Post Posted December 23rd, 2005, 5:00 am

I have never received the above message with the prior versions of firefox. I have a high spped connection on cable. Since installing 1.5, I see this message often. Is there a fix or should I go back to a prior version. PS: I have used firefox since it was first introduced. Thanks for your help

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Post Posted December 23rd, 2005, 8:47 am

What exactly does the error say and which sites do you see it on?


Post Posted December 24th, 2005, 12:45 pm

I get the message "server not found". I get it at different sites that I go to when surfing the web. The error message aslo gives you the option of trying again.(sometimes it works and other times not. Thanks


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Post Posted December 24th, 2005, 2:05 pm

One reason for this is an error in domain name resolution. Firefox needs to look up the address in the domain name system (DNS) to get the proper numeric address of the server. Problems with DNS resolution can result from configuration of your network connection, problems at your ISP, or problems at the destination site's ISP. One handy site to test whether it is your DNS or someone else's is

Paste the entire host name (e.g., or or into the upper right box labeled "DNS lookup", make sure the type is set to A, and then click Lookup.

You should get a description of the process used to find the numeric address, and then a table with the answer. Note that clicking that numeric address does not take you to the site, but instead looks up who "owns" that address (often a large ISP). If DNS Stuff finds the address, you can test whether Windows can find it (this assumes you use Windows XP, 2000 or 2003):

Open a command window using the Start button, Run..., cmd <enter>
Then run nslookup, for example nslookup <enter>
The address should match the one you found at DNS Stuff. If it doesn't, there is a problem with your own network configuration or your ISP.

If it's all good but you still get this error, check your Firefox proxy server settings under Tools>Options..., General tab, Connection Settings button. "Direct connection" probably is best for your setup.


Post Posted December 25th, 2005, 7:19 am

I have dialup, just upgraded to Firefox 1.5 and I get the same "server not found" message a LOT. Does not matter what site, what type of site, nothing. And, like "guest" said you have the option to retry and sometimes it works, sometimes it doesn't. There is nothing uniform about the issue. I can close out the browser, open it again and it'll go right to the site. Then 15 minutes later it's "server not found" again. And this has started just since I upgraded to 1.5. AND, as if surfing was not slow enough previously with my lousy dialup, it is 100% slower now that I've upgraded to 1.5. I've uninstalled it all, downloaded and tried again and it's all the same. I've just started searching for solutions here on the forum so all my whining might be for nothing and I"ll find the answer but right now surfing SUCKS. Btw, I can go to.....ahem........sorry......IE and have no trouble getting a webpage....but IE sucks worse than anything so I'll suffer for now!


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Post Posted December 25th, 2005, 8:31 am

jscher2000 - I had never seen before. A neat and useful tool, thanks.
[Edit, Feb 2007: is now a subscription service. A free subset of tools is still available, but requires free registration.}

cyounow and MickeyCook - Here's how all this works, for ANY browser:
  1. You enter a URL you wish to go to (or click on a hyperlink).
  2. The internet can't use the alphanumeric domain name (e.g. , so the browser sends a query to your operating system to look up the address for that domain name.
  3. Your operating system sends the request to the Dynamic Name System (DNS) server which your system is configured to use. Typically this is a DNS server at your internet provider, but it could be elsewhere.
  4. The DNS server looks up the domain name and returns the numeric IP address (e.g. = to your operating system, which passes it on to your browser.
  5. Your browser THEN actually sends your request out to the given IP, again through your operating system.
This all happens in the background and it's usually pretty quick so you're not even aware of it. It's sort of like when you want to send a postal letter to somebody - you can't just put their name on the envelope, you must look up their mailing address first.

When the DNS lookup fails, you receive a "server not found" error message in FFox (or "We did not find results" message in MSIE) . This either means the domain name you are requesting does not exist, or that the DNS lookup failed for one reason or another.

Note that the browser can only request that the DNS lookup take place, and then the process is handed off to your operating system and then to the DNS server for execution. So it is essential that the DNS process, which is not controlled by the browser, works quickly and efficiently in order for your browser to be able to access sites well. There are a number of different things that can interfere with this, however.

Most of us today will have some OTHER software installed on our systems that can interfere with the internet access. Firewalls, antivirus programs, and proxies all intercept these calls and are responsible for passing them on. In many cases, these other programs will not work well with a new browser (or sometimes even with an updated version of the same browser) until they have specifically been configured to pass these internet calls from your browser through. And it is also true that many of them will work with Internet Explorer right out of the box but must be manually configured by you to work with FFox.

One very common problem with security programs occurs after you have updated to a new version of FFox. Your firewall or other security program may recognize that this is no longer the program you have authorized to access the net, and thus blocks Firefox's attempts to do a DNS lookup. One generally needs to remove all the Firefox permissions from the firewall configuration and let the firewall rediscover Firefox and ask if you want to give Firefox permission to access the net. See this Mozillazine article for more information on configuring firewalls:

It also has been reported here, many times, that an update to one of these utilities can cause them not to work correctly with FFox until the utility has been reconfigured to recognize FFox again. This is not FFox's fault, but deals with how the utility itself is coded. Parts I, III, IV of this post may be quite helpful in dealing with such issues:

As for the DNS lookup itself, by default, FFox uses the most recent version of the IP spec, IPv6, to make its DNS requests. Some older DNS servers don't handle this very well, resulting in some DNS requests working and others not, seemingly randomly. If this is your situation, and some other browser doesn't seem to have the problem, it may be that the other browser is still using the older IPv4 protocol. You can disable IPv6 support in FFox, thus causing it to fall back to IPv4 that all servers should be able to handle, as follows:

- enter about:config in your URL/Address bar
- enter ipv6 in the filter field
- double-click on network.dns.disableIPv6 to toggle this to true

This will only help if poor IPv6 support by your name server is the source of your problem, and this should get less and less common as servers are updated, but it's an easy thing to try and should not cause any problems. If you see no improvement, you can always toggle the setting back to false.

For help with other DNS problems, please see Part II of the same post I referenced earlier:

[Edited to add additional information and improve clarity of expression.]
Last edited by makaiguy on September 10th, 2009, 5:31 am, edited 3 times in total.
Doug Wilson, "The Makai Guy"
Win10 (64bit): FF 73.0 (64bit), TB 68.4.2 (32-bit) ║ Android 8.0/7.1.1: FF Mobile 68.5.0, No TB for Android available, dammit!
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Post Posted February 22nd, 2006, 1:57 pm

If you are using Windows, there's one other catch. Windows will try only once to get an IP address, and it caches the result. This is a problem if it doesn't succeed the first time, because it just tells the browser that the address could not be found, without trying again until a timeout period has elapsed. This post tells what to do about it.
Last edited by VanillaMozilla on July 25th, 2010, 8:48 pm, edited 1 time in total.

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Post Posted February 23rd, 2006, 1:12 pm

Look, this started when I upgraded to the 1.5 version. And to go thru all of that DNS stuff seems like a lot. Plus to be perfectly honest I am a bit frustrated because, although I could build a computer and run installs & set ups like a Mother...all of that internet protocol stuff is really beyond me. As much as I hate to admit it "I am packet route ignorant" So a lot of what you posted isn't intuitive to me. I am really afraid when I don't fully understand what steps I am making changes with. So 2 things I need if you please? 1) Do you know what is precisely causing this "Server not found" Issue with the newest Firefox. and 2) Can you point me to a URL that can teach me "packet routing basics"?
I really, really hate being out of the understanding loop when I do something...especially on my computer!

Thank You

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Post Posted February 23rd, 2006, 1:30 pm

Look all I know is earlier versions of Firefox worked PERFECTLY with the same exact system and configurations. Nothing has changed except the "Updating of Firefox version" So obviously its not the OS, the router, or my connection. I am sorry but I can't become a "Internet expert" or "Specialist" just to run a browser after 8 years of "Not having to do any of that!" So if anyone gets a "Solid reason" for this server not found/ try again (Always to no avail if you do "try again") with the new version of Firefox, please let me know. Until then, I will revert back to a earlier version of Firefox, or even use IE as much as I hate to! But I'd rather do that then be locked out of 4 out of 15 sites. After updating Firefox "Server not found" comes up more now than it did back in 1996 with a Dial up line and MSIE 3!

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Post Posted February 23rd, 2006, 1:52 pm

"It burns like hygiene!"


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Post Posted February 28th, 2007, 7:58 am

[duplicate post removed]
Last edited by makaiguy on July 22nd, 2010, 5:45 pm, edited 2 times in total.
Doug Wilson, "The Makai Guy"
Win10 (64bit): FF 73.0 (64bit), TB 68.4.2 (32-bit) ║ Android 8.0/7.1.1: FF Mobile 68.5.0, No TB for Android available, dammit!
What a fool believes he sees, no wise man has the power to reason away - Doobie Brothers

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Post Posted February 28th, 2007, 8:45 am

Let me simplify it for you. Firefox works through the operating system (as do ALL Internet programs). Your operating system does this, NOT Firefox. The operating system passes messages to and from the Internet, and if the local Internet isn't working quite right, you will have a lot of connection failures. Note added later: It's possible for Internet "security" programs to mess up Internet access for Firefox. Again, there's nothing Firefox can do about it.

Here's how it works. The domain name server is like a telephone directory, except that it works automatically. You look up a name and you get the phone number. A URL is the name and the IP address is the phone number. You can't make a phone call without the number, and you can't do anything on the Internet without the IP address. Ordinarily your OS gets the number automatically from a special server (domain name server, or DNS) that is usually supplied by your Internet service provider. It's common for the DNS to get too busy and slow down, especially if the service is very cheap or they have just gotten a bunch of new subscribers. If service is too slow, the operating system gives up on waiting, and times out. But the quality of service can be erratic, working fine one day and poorly the next. So you may think you have fixed the problem, but find later that what you did has nothing to do with it.

One other thing. What often happens is that you try once or even twice, and you don't get a connection. Then you try again (with the same browser or another browser) and you get an instant connection. That's because the IP address has FINALLY come in, and it's cached in at least 3 places so it's instantly available.

Without seeing your computer or spending more time than I have, I can't say for sure whether that's your problem, but from your description that's by far the most likely cause. You can change your DNS system.

I'd say try the IPv6 trick. When that doesn't solve the problem, read the links that were already given. And here's another one to read: ... bsites#DNS and follow the links. Get Trolly's WinDNS tool, so you can look up IP addresses yourself and see how your DNS service performs. There's a spectacular success story to read about. (Hint: remember what I said, that DNS lookups are cached, so lookup is fast the SECOND time.) When you get an IP address, you can use it in the browser.

Sorry, it means reading and figuring it out. We can help, but have only so much time to spend on this. I've spent hours and hours on this explaining it to other people, and I can't do it for each one. Once we can convince them to check it out (and convincing them takes a lot of time), they are often amazed.
Last edited by VanillaMozilla on August 1st, 2010, 8:21 pm, edited 1 time in total.

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Post Posted August 1st, 2010, 6:55 pm

OK, I read the reference provided. If the problem were related to a firewall, I would never be able to access the internet with FF. However, if I click "Try Again" several times, I do finally access the internet. Then, if it were a question of firewall, a given computer would always have the same problem regardless of ISP. This is not the case. A given computer, when accessing the internet on one ISP always has the problem when using Firefox (never when using Opera or MSIE). the same computer always has the problem on another ISP. I disabled isvp6. In fact, that did have a positive effect, but it did not eliminate the problem. It is apparent to me that there is a compatibility issue between Firefox and my ISP. The problem does not reside on my computer and the problem is not a product of user error. Since I am not the only person to experience this problem, I have to conclude that there is a problem with Firefox. As I have said, I never encounter this problem with MSIE. I recently downloaded Opera and never encounter it with that program.


Post Posted August 1st, 2010, 8:12 pm

The thread you are replying to is a dead thread from 2007. You should start a new post with your symptoms.
Also, you are wrong about firewalls. One would think that a firewall would either "allow" or "not allow" but that is not how they behave. They very often only interfere with page loading once in a while. Unless you are a "super expert" computer user, I would advise you not attempt to use any software firewall. A hardware firewall or NAT built into your router will protect you from external attacks, and antivirus software is the most practical way to protect against your own computer leaking. Software firewalls are a good idea in theory, but a lousy idea in practice. Reading the thousands of threads of people with firewall problems here you will see that they cause far more problems than they could ever prevent.

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Post Posted August 1st, 2010, 8:35 pm

pkafer wrote:It is apparent to me that there is a compatibility issue between Firefox and my ISP.

There is no such thing. An Internet connection transmits data packets according to a well-defined standard called Transmission Control Protocol/Internet Protocol (TCP/IP). Pure and simple. Nothing more, nothing less. It interacts only with low-level functions in your OS, but not with programs like Firefox. And with 300 million users and well over 10 years of use, you can be sure that Firefox is "compatible" with the Internet.

The problem you described is usually caused either by some demented "security" program (these programs have errors too) or by your DNS. If you try Firefox first and then try another browser if Firefox fails, it will often appear (incorrectly) that Firefox has the problem but the other browser does not, when the actual problem is that the server or the Internet is slow in responding. You really do need to start another thread. You probably will not get much response on this one. And I've helped you all I can.

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