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I am using Firefox 4.0 on Windows Vista - 32 bit. There seems to be some backward compatibility issue when I open a url:

Then enter my login credentials, it gives an error as below-

Remote XUL: This page uses an unsupported technology that is no longer available by default in Firefox.

It's strange because, The same url & login works fine on a earlier firefox version 3.6 or so on a Windows-Vista.

1) Isn't there any setting like 'compatibility mode' in Firefox which would allow sites using some older technology or whatever causes the mismatch to work correctly?

2) Any fix for this particular error I am facing?

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up vote 1 down vote accepted

Verbatim from

Here are some options on how to fix it:

  1. You can log in under the Simple or Basic interface without the error coming up.

  2. Go to this link: and download the addon. Once this is installed you will need to go to Web Developer (or Tools on the Menu Bar) then down to Remote XLU manager. Then add in mail.YOUR-DOMAIN-NAME.COM and this will let you log in again under advanced interface without error.

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Thanks soln 2. Worked fine. What is solution 1. you mentioned - 'Basic interface' That url which I am getting error at doesn't have any other interface. – goldenmean May 3 '11 at 21:48
That's not an FF feature (sadly) so a basic mode would have to be defined through the host. – Blomkvist May 3 '11 at 22:08

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