What do you see on the page? Do you see "Technical Information" or "I understand the risks" like the link below?

https://support.cdn.mozilla.net/media/uploads/gallery/images/2011-10-19-09-09-25-5809bb.jpg

Oh I'm sorry I wasn't clear!

It says "Technical details" followed by this information when I click on it:

"www.facebook.com uses an invalid security certificate.

The certificate is not trusted because no issuer chain was provided.

(Error code: sec_error_unknown_issuer)"

It doesn't have the "I understand the risks" link below that.

A few suggestions:

(1) Are you using any proxy services? You can bypass those here:

orange Firefox button (or Tools menu) > Options > Advanced

On the Network mini-tab, click the Settings button, then choose "No Proxy" and OK out.

Does that make any difference?

(2) You might also need to check your extensions, since they can change how Firefox accesses sites. Unfortunately, those were not listed along with your plugins.

You can use the following page to disable ALL nonessential, unrecognized, or unwanted extensions, then restart Firefox and see whether you can access Facebook.

orange Firefox button (or Tools menu) > Add-ons > Extensions category

Any change?

(3) In case the problem is cached files, you can clear your cache.

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

Cache

You can clear Firefox's cache completely using:

orange Firefox button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

Cookies

You can open the dialog using:

Alt+t (opens the Tools menu) > Page Info > Security > "View Cookies"

In the filter box at the top, change the site to facebook.com

Then remove the cookies, OK out, and try reloading the page. Does that help?

If "I Understand the Risks" is missing then this page may be opened in an (i)frame and in that case try the right-click context menu and use "This Frame: Open Frame in New Tab".

• Note that some firewalls monitor (secure) connections and that programs like Sendori or FiddlerRoot can intercept connections and send their own certificate instead of the website's certificate.
• Note that it is not recommended to add a permanent exception in cases like this, so only use it to inspect the certificate.

Wait, where is the context menu?

I'm not using any proxy blocker, I just upgraded my laptop so I haven't downloaded any extensions yet. I'm not sure what's going on with Firefox, at first every website was blocked (even google searches), though I was able to add an exception. And now, facebook is blocked without having the ability to add an extension, and I am unable to download things (like my Nook for PC) but am able to do so on other browsers. I'm going to try clearing my cache and cookies, but this is very strange. I've been using Firefox for 12 or 13 years loyally, without fail --so I'm extremely familiar with the browser. I've installed it so many times, on several different computers and operating systems, THIS has never happened.

Edit: Clearing the cache and cookies did work --I was able to set an exception to facebook. Still don't understand why this happened. Firefox has never given me these problems before (problems with download, graphics etc). It's very strange.

The context menu is the menu that opens if you right-click with the mouse.

• Note that it is not recommended to add a permanent exception in cases like this, so only use it to inspect the certificate.

Check the date and time in the clock on your computer: (double) click the clock icon on the Windows Taskbar.

Check out why the site is untrusted and click "Technical Details to expand this section.
If the certificate is not trusted because no issuer chain was provided (sec_error_unknown_issuer) then see if you can install this intermediate certificate from another source.

You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.

• Click the link at the bottom of the error page: "I Understand the Risks"

Let Firefox retrieve the certificate: "Add Exception" -> "Get Certificate".

• Click the "View..." button and inspect the certificate and check who is the issuer of the certificate.

You can see more Details like intermediate certificates that are used in the Details pane.

If "I Understand the Risks" is missing then this page may be opened in an (i)frame and in that case try the right-click context menu and use "This Frame: Open Frame in New Tab".

• Note that some firewalls monitor (secure) connections and that programs like Sendori or FiddlerRoot can intercept connections and send their own certificate instead of the website's certificate.

Thanks.