Are you posting from the problem system? I don't see anything in your "More system details" that immediately jumps out at me as a problem.

Could you check the Error Console (Tools menu). Use the Clear button in the console, reload the problem page, then check the console for red X icons indicating scripting errors. (You shouldn't see any.) Then click one of the tabs and see whether you get an error. Anything??

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Also, can you compare the settings in any external security software? Some include web filtering features that could, at least in theory, strip out scripts from pages or block scripts that load from a separate file.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

Thanks to both of you for replying - hope the following is helpful:

Tried the Error Log first and yes, getting lots of errors when opening the site and when navigating around it. All errors suggest syntax errors in the JavaScript itself? eg:

Warning: Expected declaration but found '#padding-top'. Skipped to next declaration. Source File: http://www.scan.co.uk/css/scan.css?303 Line: 295

Or:

Error: jQuery is not defined Source File: http://www.scan.co.uk/js/jquery.ui.mouse.min.js Line: 17

Obviously this can't be the problem as it wouldn't work on other PCs. So tried a different tack:

I tried using MS Internet Explorer 8/64 instead and when I opened the site got this warning on toolbar:

"To help protect your security, Internet Explorer has blocked this website from displaying content with security certificate errors. Click here for options..."

When I select the option to "Display blocked content" everything including JS works fine.

So is the problem with certificates?

Other info:

Tried Safe Mode but that made no difference.

Regarding security software, I am running MS Defender and Avast Anti-Virus, Windows Firewall and Spybot-SD Resident. I've heard that running 2 a/v programs together can cause problems so have turned off MS Defender Real Time scanning but that didn't make a difference. Should I stop it completely?

Anything else you need guys?

Kind Regards, Terry

Great detective work: the page does use a Google script that is retrieved using a secure connection. Do you get an error going directly to the page?

https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.js

If so, what is the error message?

With a specific message, this article might help: Secure Connection Failed | Troubleshooting | Firefox Help.

It's a good idea to have exactly one real-time antivirus scanner. I think Defender is more of a spyware scanner, so it probably can coexist with Avast.

Hi jscher2000, Went to that website and got following error message:

"This Connection is Untrusted

You have asked Firefox to connect securely to ajax.googleapis.com, but we can't confirm that your connection is secure. Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified."

I've looked through your other link but can't find anything I haven't already tried. I've also searched via Google and notice that this was a problem on earlier versions and clearing the cache fixed it, but didn't work for me.

I would be interested to see if others have problems with this site using FF. It is the on-line shop for a very large and trustworthy computer spares company here in the UK, so safe to go there. URL is http://www.scan.co.uk

Getting frustrated over this now - had to use IE to order a new drive today and I normally avoid that program like the plague!

Regards, Terry

We're getting closer. What is the detailed explanation Firefox gives for not liking the certificate? It should display when you click Technical Details.

Also, do you have different proxy settings for IE and Firefox?

Sorry but I'm getting out of my depth here! I'm not used to IE so you need to tell me how to check proxy settings. FF is set to "No Proxy"

I don't get an error message from FF to say it doesn't like the certificate and can't see where you click "Technical Details"?

Please leave more info on this - am signing off today now but will reply tomorrow. Many thanks for your help an patience.

Kind Regards Terry

I don't get an error message from FF to say it doesn't like the certificate and can't see where you click "Technical Details"?

Sorry, you have to go back to the direct link to Google for this one:

https://ajax.googleapis.com/ajax/libs/jquery/1.6.0/jquery.js

I notice that I have two Google Internet Authority certificates in the Certificate Manager under Equifax. One has expired last year (06/20/2010) and the other will expire in 06/07/2013, so is still valid. So it may be worth to check that out.

This is the response from FF when clicking on Technical Details:

ajax.googleapis.com uses an invalid security certificate. The certificate will not be valid until 27/05/2011 02:22. The current time is 09/05/2011 09:19. (Error code: sec_error_expired_certificate)

And response from IE:

There is a problem with this website's security certificate. The security certificate presented by this website has expired or is not yet valid. Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.

 We recommend that you close this webpage and do not continue to this website.  
 Click here to close this webpage.  
 Continue to this website (not recommended).  
    More information: (Selected)

If you arrived at this page by clicking a link, check the website address in the address bar to be sure that it is the address you were expecting. When going to a website with an address such as https://example.com, try adding the 'www' to the address, https://www.example.com. If you choose to ignore this error and continue, do not enter private information into the website. For more information, see "Certificate Errors" in Internet Explorer Help.

Hope that helps.

Cor-el, Sorry but don't understand your message in relation to my problem?

Kind Regards Terry

This seems to indicate a problem with the Windows system clock, or Firefox's ability to read it:

The certificate will not be valid until 27/05/2011 02:22. The current time is 09/05/2011 09:19.

Man - you are a genius! System clock was set to 9th May not 9th June - just updated it and the Scan web site now works - unbelievable!!

I've got the clock to sync with an internet clock so never think about it. Great pity that the FF error codes are not more helpful?

Many, many thanks for your help and patience.

Kind Regards Terry

It would be useful if you got some kind of "infobar" about the invalid certificate for the script when it is only a small part of the page. Maybe that can be implemented in the future.