It's possible that one of your add-ons (of which you have many privacy add-ons) is blocking the site, it works for millions of users a day.

Maybe try testing a fresh Firefox profile? Profile Manager - Create, remove or switch Firefox profiles

I'm not seeing a plugins section the System Details list next to your question, so it is likely that this list is blocked somehow.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

(plugins are not affected by Firefox Safe Mode)

Whitebuck said

When I go to "Tools" / "Plug-Ins" and click on "Check To see If Plugins Are Up To Date" it goes to Mozilla Check Your Plugin Page, but fails to show plugins or checked plugins update status. ( https://www.mozilla.org/en-US/plugincheck/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=plugincheck-update ) I am using OS X 10.10.3 / Firefox 37.0.1 / March-14-2015 Tried, re-installing over original, clearing cookies, clearing cache and starting in Safe Mode to no avail. Another ridiculous oversight and there's never any support for when things do go awry. Unfortunately, I have received no professional concern, with a competent cause and cure. none. And I have had and reported this problem since Firefox 35.0. Need info and a fix, for Months Now! Thanks! Whitebuck Still wondering why, you're losing users?

Whitebuck said

When I go to "Tools" / "Plug-Ins" and click on "Check To see If Plugins Are Up To Date" it goes to Mozilla Check Your Plugin Page, but fails to show plugins or checked plugins update status. ( https://www.mozilla.org/en-US/plugincheck/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=plugincheck-update ) I am using OS X 10.10.3 / Firefox 37.0.1 / March-14-2015 Tried, re-installing over original, clearing cookies, clearing cache and starting in Safe Mode to no avail. Another ridiculous oversight and there's never any support for when things do go awry. Unfortunately, I have received no professional concern, with a competent cause and cure. none. And I have had and reported this problem since Firefox 35.0. Need info and a fix, for Months Now! Thanks! Whitebuck Still wondering why, you're losing users?

Thank you, Tyler Downer

For your create a new Profile suggestion, corrected the problem.

After creating a new Profile and testing the web page for proper functionality. I reinstalled my Persona and all but two of my originally installed Extensions and the "Check To see If Plugins Are Up To Date" web page continued to load properly. Obviously there was something in the old Profile which prohibited the Web Page from loading properly. What that was, will unfortunately remain a mystery.

For those who may suffer the same problem. I forgot to mention . That I also had to import my Bookmarks and manually re-populate my Bookmarks Toolbar. The complete process was rather extensive and time consuming.

Glad to hear it!

If you still have the old profile then you can try to delete the pluginreg.dat file and possibly reset all prefs by deleting or renaming the prefs.js file.

Thanks, cor-el

Deleting "prefs.js file" and "pluginreg.dat" in my previous Default Profile, worked as well. And it was an easier and less time consuming fix. Compared to creating a new Profile.

But, in retrospect, I am glad I created a new Profile and reconstructed the Browser.

For now, I have an extra Profile, if needed, for an unforeseen future event.

I'd like to point out that this page only stopped working recently - since it was changed

CHANGE IT BACK and don't use multiple scripts on multiple domains in an unsafe manner.

Optimizely and gravatar are banned from my browser for privacy reasons, do not use it.

Thanks Kvoter, for the information!

I should of included a far more easy solution:

For flash: Tools -> Add-ons -> plugins, manually take note of plugin version and for safety set plugins to 'never activate' or 'ask to activate'

then compare version, flash here: Adobe Flash Player Download

For other plugins simply google "get [plugin name]"