11 March 2010

"Server not found." Firefox can't find the server...

This is VERY annoying.

For the past several weeks my blogging has been hampered by recurrent appearances of the error screen shown above.  It shows up when my computer (2-year-old iMac) suddenly and inexplicably seems to be unable to access the internet, and the "try again" button does nothing.  If I quit and restart Firefox (I'm using 3.5.8), the problem still persists; I have to restart the computer in order to get online again (and from force of habit I usually zap the PRAM on a reboot, but don't know if that's necessary).

The problem is apparently not in our cable access or the household router; other computers in the house work fine when this problem appears.  And it's not just Firefox, because when it happens I can't solve it by switching to Safari or other browsers, which show their own "server not found" error messsages.  The computer itself is not frozen; I can switch to other tasks.  And I can even scroll and bookmark the pages I have open - I just can't go anywhere else.

When I searched this message I found some forums suggesting it happened because of conflicts with plugins, so I've temporarily disabled by Adblock Plus, my Flashblock, and my NoScript - but that hasn't solved the problem.

I think this has something to do with my websurfing style.  I use tabbed browsing, and typically open 15 tabs at a time looking for TYWKIWDBI material.  If I leave them open a long time (while checking sublinks etc), or if I walk away to have lunch and then come back, that's when the problem most often occurs.  This kind of response reminds me of the old days when the RAM used to get "used up", but my iMac has a gigabyte of RAM, and I'd be surprised if that per se is the problem.  But maybe.

If anyone else has experienced this and knows a good workaround (or a way to prevent it),  I'd love to hear from you.


  1. Not sure if this will help but running a registry cleaner every couple of days and a program called "Clean up!" (love that flushing toilet sound, by the way) tends to keep the browsers trouble free. Check for any malware, I know that it can sometime cause browser/server problems. Good luck.

  2. if you get the error screen, try accessing google via

    if that works, you will know that it's your DNS that is fucked up.

    one easy fix that might help then would be to flush your dns cache:

    In Mac OSX Leopard, you can use the command dscacheutil -flushcache to flush the DNS resolver cache:

    bash-2.05a$ dscacheutil -flushcache

    In Mac OSX versions 10.5.1 and before, the command lookupd -flushcache performed the same task:

    bash-2.05a$ lookupd -flushcache

  3. I have this same problem. I'm glad it's not just me; I thought it was an issue with my modem or ISP. I work with umpteen tabs at the same time, too.

  4. Wow! I am a long-time reader of this blog - what a cool (if unfortunate) coincidence that you are having the same problem I have been having for the last month or two. I thought it was just me.

    I have a three-year old MacBook with, I think, 2 gigs of RAM, and I also typically have many many tabs open at once. This problem comes up most often when I am trying to watch streaming video, e.g., on Hulu. I hope if you find a solution you'll publish it here, as I suspect with your readership you are far more likely to hear from someone in the know than I am.

    Good luck!

  5. I have similar issues and I have a 2007 Dell Windows Vista, but use Firefox. I, too, have multiple tabs open; tried clearing my cache - no luck. I look forward to coming back to the comments section for tips. Thanks!

  6. Same issue...always just assumed it was my connection. I know that it has gotten longer in duration within the past couple of weeks

  7. I have this problem on my Dell, and I am 99% certain it's an issue with the network card. When I open too many outbound connections the card just gives up and I have to reboot the computer to get it working again. I imagine you have the same or a similar problem with a faulty card or crap drivers for the card. You could try making sure your network card drives are up to date.

  8. Misery loves company. In view of the immediate outpouring of comments from people with similar problems, I've changed the title of the post to incorporate the text of the error message, which will steer more people this way when they search.

    Now, we'll see if the collective mind here can come up with a solution.

  9. Same issue on both my PC and my Mac.

    Same extensive use of Tabs.

    Interestingly though my Wireless Network Card cannot even find my previous network, but can find all other nearby networks. And others using the router can still access it.

  10. Have you gone to your file: in your display menu and looked to see if your work offline is checked?

  11. Is it a wired or wireless network connection?

  12. I just stopped using firefox altogether and it solved several problems including the one you are talking about.

  13. I've seen that happen with my wife's mac, but it only does it when one of our kids uses it. He uses a TON of bandwidth (multiple chats, video chat, internet radio, myspace, facebook, etc. all running at once), so you might be on to something with your hypothesis about the number of tabs and memory you're using.

    If you're using wireless, the easiest fix for the problem is to turn the airport off and then back on. You shouldn't need to reboot the whole computer.

  14. Anonymous said...
    > if you get the error screen, try accessing google
    > via

    > if that works, you will know that it's your DNS

    This is good advice as it sounds like you're connected but can't look up a site. I would go to System Prefs then Network then click the Advanced button then click the DNS tab. I use the Google DNS servers, which are and

    You may be getting your DNS settings from your router, and that may be were the problem lies. If you use "local" settings you should hopefully not have the problem again as long as your internet connection is working.

  15. @Seth - thanks. My preferences showed three DNS servers, so I added the two Google ones. Do I need to "select" them, or does the system revert to them automatically if the other ones fail?

  16. I'm pretty well going to assume all of you are using a wireless connection (although it can happen in wired too, but much more rare).

    At the output end of every wireless card, just before the antenna, is what's called a "final." This is a transistor used as part of the amplifier circuit to crank up the power of the data signal before sending it to the antenna itself. These are subjected to some grueling punishment of being cycled hot to cold on a regular basis, and as a result, all of them eventually die.

    But they don't die in a moment, or even overnight. Often they become unstable over the course of several months until you're tearing your hair out trying to figure out just what the heck is going on. One moment everything is fine, the next it starts to act up, you fiddle around with it, and think you've fixed a problem. A bit later it's all trouble again.

    It will happen to every single wireless card given enough time (and assuming something else doesn't kill it first).

    Try a USB wireless card and disable (or remove, for those that can) the old wireless hardware. See if things stabilize.

    I swapped out the whole amplifier circuit on a card that had gone rogue on me like that using a 1 watt transistor just to mess around. Worked, but I had no way to crank up the signal on the particular card so it wasn't terribly useful. Now use a standard external 1W antenna hacked in to a wireless USB adapter that I use to connect to nearby restaurants when my cable goes out.

    Pic of the hack: http://gesare.com/uploads/1w-wireless.jpg

  17. The first step would be to download an alternate browser, like Opera, and determine whether the problem occurs with it as well.

    That way, you can isolate the problem to either the OS or the browser.

  18. Thanks for the comments, everyone. I'm the same person as Anonymous #3 up top, and I have a wired connection through a modem box. Time Warner came to check it out, replaced the thing, my problem is certainly happening less often now but it has not been fixed.

    I've tried watching things on Safari and the same thing happens.

    How's Google Chrome as a browser - shall I try it?

  19. Had the same problem, found that it was a conflict between a virtual LAN network I had running and my home network. After disabling the virtual network my connection works fine. Seems to be that multiple networks running at once can cause the problem.

  20. Check your activity monitor in Utilities. Firefox is a bit of a memory hog, and having multiple tabs open increases usage.
    If you need multiple tabs open, you might want to revert to Safari.

  21. @Seth: Similar situation and I had change my primary DNS server on my router to the Google DNS

    You can check the speed of various DNS servers using namebench (http://code.google.com/p/namebench/). This program will tell you what the most efficient DNS server is available

    @Minnesotastan: it should automatically use the new DNS server as long as the Google DNS server is set as the Primary.
    You should flush your DNS to be sure.

    See Anonymous' post for macs. For Windows: go to command line (Start button, then Run, type cmd, press OK) and run the command: ipconfig /flushdns

  22. Try simply unplugging your modem...waiting 10 seconds...then plugging it back in. Worked for me with a totally similar situation (24" iMac)

  23. Here's my followup; others may want to offer their own comments re workarounds they've tried.

    First, re some questions I was asked. @Pietr, I have occasionally seen the "work offline" box (automatically?) checked, and had to uncheck it, but that is not always (or typically) the case. @nolandda, my connection is wireless. And @anonymous I'm reluctant to turn Airport off; I've seen comments from people who had difficulty turning it back on - but it probably would work.

    Now first, re Sue's suggestion to check my Activity Monitor. I did so, and to my surprise discovered that with a dozen tabs open I had only about 50-80 MB of memory vacant, and when I then turned on Word (as I sometimes do when blogging), it plunged to a miniscule 8-10 MB. Out of a capacity of 1 GB of RAM. So that's probably part of the problem.

    I've had the lockup occur once (just a few minutes ago) and I followed the suggestion to try accessing Google via When I hit return, nothing happened for a long time, then I got a message "The connection has times out." So I tried again - and got connected! From that I assume that at least part of my problem is with the DNS server. I haven't quite figured out how to enter the commands to flush that cache, but will try to do so later. My 14-year-old niece will be here for a visit next week and can help me with some of these more complicated computer maneuvers.

    1. Update 2012. This particular problem did not recur for me after this post, but the lack of memory eventually led to other problems. In 2012 I finally had to add 2 more GB of RAM for a total of 3.

  24. I go to school and use a brand new Mac Pro, very powerful machine, top of the line. I get the same problem when I haven't been on for a break, or lunch. I hit the try again until it finally pops up, it takes about twenty to fifty clicks but eventually it always works. Its a Mac/Firefox ordeal.

  25. I had the same thing happen, it improved when i added opendns servers, and was fixed when i uninstalled peerguardian which i completely forgot i had installed

  26. Apparently this issue is going to be fixed in the next 10.6 update (10.6.3). I'm willing to bet you're running snow leopard, perhaps? Anyway, we university types have been plagued by this issue (on all browsers) since the last snow leopard update (having to do with how our computers connect to a secure wireless network). The update should be out any week now, and I hope that it fixes all of our problems.

  27. I use a 3 year old HP Pavilion dv2000 and I had the exact same thing happen over the winter...

    We had a wireless network aboard this yacht I crewed on (no cheapy, a 125' $15 million job) and had the same exact symptoms.

    I, too, like to keep multiple tabs open in Firefox but our net connection was so slow via satellite that I reduced that number to only 4 or 5 tabs.

    Symptoms always occurred after I let the computer sit for more than half hour or so.

    Same deal, I had to reboot. Everything else worked fine, but no browser I opened could connect.

    Now back to a land based cable modem/wireless setting, no interruption whatsoever; can leave the machine for hours day in/day out and always have a connection...

    Does this help? I never stopped to figure out what was wrong, just kept rebooting when it happened and it drove me MAD!

  28. It doesn't seem to be the DNS server per se. I run my own DNS server, and I can log onto the DNS and the query always (*always*) works just fine. When I go back to Windows (or any application in Windows), it continues to say that the hostname is not found.
    - Other hostname lookups work from the same browser
    - The problem goes away in about 10 minutes
    - Some hostnames cause this problem repeatedly (schoolloop.com, questionablecontent.net) Others almost never.
    - The problem is more frequent when I open a lot of tabs simultaneously.

    My conclusion is that a slow DNS response leads to the hostname not found result, and there is some service in Windows that will not try another hostname lookup within the timeout window of about 10 minutes. The "Try Again" button in Firefox sends another query to Windows, but Windows does not send another query to the DNS. But how do I reset that Windows service without rebooting Windows?

  29. I am with Mathrec on this. After a while (5min-20min) all my browsers, IE, Chrome, Firefox run into server not found... after 10-thousand re-tries I get lucky once in a while. System requires a re-boot to resolve. All other PCs connected to the router work just fine, so the problem has to be windows!

    "ipconfig /flushdns" did appear to help; but I have not checked this thoroughly.


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