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Why is Firefox not accessing some sites when safari on the same machine has no problem.

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There is a growing number of sites that Firefox can no longer access. One is a bank, another is Waterstonesmarketplace. I can however use safari in both cases to access these sites. This never used to happen, but now Firefox seems to be getting worse. Access to the bank account times out. Access to waterstones says I am using a wrong DNS server, which is wrong.

There is a growing number of sites that Firefox can no longer access. One is a bank, another is Waterstonesmarketplace. I can however use safari in both cases to access these sites. This never used to happen, but now Firefox seems to be getting worse. Access to the bank account times out. Access to waterstones says I am using a wrong DNS server, which is wrong.

All Replies (8)

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Try to disable IPv6 (check for other possible causes as well).

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Have now tried the same attempts on another machine in the same room. On a macbook pro. This macbook has no problem with safari, but Firefox can access www.waterstonesmarketplace.com but not onlinebanking at ABNamro. On the imac Forefox cannot get to Waterstones and intermittently gets to ABN.

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peter.gilks said

Access to the bank account times out. Access to waterstones says I am using a wrong DNS server, which is wrong.

What is the complete wording of the DNS server message? Usually the DNS servers used are determined by settings in your router / cable modem / DSL modem. However, that can be overridden at the OS level and within a browser's settings.

Did you already work through the various suggestions in the support article that cor-el linked to?

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I have seen no suggestions which solve the problem other than stick to safari

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You're right, I had more questions than answers because your Firefox is behaving in a nonstandard way and I don't know what the problem is yet.

What is the complete wording of the DNS server message? Usually the DNS servers used are determined by settings in your router / cable modem / DSL modem. However, that can be overridden at the OS level and within a browser's settings.
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Oh wait, you posted that information in a different thread. To avoid running us around unnecessarily, can you please stick to this one thread?

You are seeing this page because you are using a BT service which requires the use of BT DNS Servers and it appears that you are attempting to connect using a DNS server outside of our network.

Our BT Protect and BT Parental Controls services both require the use of our BT DNS to keep you safe online.

You may have selected a different server in your network settings or installed an application that uses an alternative service.

Click here to find out how to fix this

Is this the link given to check your DNS settings: http://bt.custhelp.com/app/answers/detail/a_id/601

I think you have three choices at this point:

(1) Report to BT that it is giving you a false message and ask them to solve it.

(2) Go into your My BT and assuming BT Protect and BT Parental Controls are on, turn them off. However, that may merely mask a real problem.

(3) Track down the source of the error yourself. The support article already covered the most obvious potential explanations. To see whether this could be caused by one of your extensions, could you test the problem sites in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the option key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

  • "3-bar" menu button > "?" button > Restart with Add-ons Disabled
  • Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

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It appears that both my machines have upgraded Firefox to 44.0.1 and the problem with online banking at ABNamro has disappeared. However I still get the same error with waterstonesmarketplace. It only occurs with this site on both machines, I can find no other site it occurs with. Safari and Brave do not have the problem. If it were a BT fault why does it only occur on Firefox and not safari and Brave. I have played with the BT Protect controls and IPv6 controls to no avail. I have had Firefox in Safe mode and this made no difference. I have looked at the DNS server on my machine and this looks correct, there has got to be something in Firefox that causes a problem. So one problem has gone but not the other.

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Hi Peter, other users diagnosing odd connection issues on Mac have mentioned the utility "Little Snitch" that tracks outbound connections made from all programs. I haven't tried it myself, but perhaps it will show some unexpected DNS requests?? There is a trial period available on their website: https://www.obdev.at/products/littlesnitch/index.html