Please turn off your Caps Lock. In text talk, this is shouting.

You say others reported problems with the Theme Font & Size Changer add-on?

Disable it and contact its support.

SORRY FOR THE CAPS BUT I HAVE POOR EYE SITE AND MY TYPING SUCKS ALONG WITH IT. REGARDING THE REMOVAL OF THE EXT THIS WAS DONE WEEKS AGO LONG GONE.I WAS JUST WONDERING IF THE EXT HAD SOMETHING TO DO WITH LOSING THIS PART OF THE PREFERENCES.ALL THE OTHER TABS IN about:perference WORK FINE.

Hi   ! This could indeed be caused by one of your add-ons (not necessarily the one you mentioned). Let's try Firefox in Safe Mode :

If Firefox is not running : Hold down the Shift key when starting Firefox. If Firefox is running : 3-bar menu => ' ? ' (at the bottom of the dropdown) => 'Restart with Add-ons disabled'. Then OK the restart. A small dialog should appear. Click 'Start in Safe Mode' ( not 'Refresh' !)

See : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

And also : https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

If that solves the problem, then re-enable the extensions one by one, until you find the culprit.

You can look at Zoom Page WE and NoSquint Plus extension to set a default font size and page zoom on web pages in case you aren't already using such an extension.

• https://addons.mozilla.org/firefox/addon/zoom-page-we/
• https://addons.mozilla.org/firefox/addon/nosquint-plus/

I installed the latest version of the TFS extension in Firefox 52.3.0 and it seems to be working fine and no problems with "Options/Preferences -> Content".

Did you check for issues with other extensions interfering like posted above (i.e. try with only TFS enabled)?

You can open the Browser Console and check for messages about extensions.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en/Tools/Browser_Console

THANKS FOR YOUR INFO BUT THE PROBLEM IS STILL THEIR.EVEN WITH ALL EXT DISABLED. AND FOR PLUG-INS I ONLY HAVE FOUR . FLASH (always active) & SILVERLIGHT(click to play) BOTH ARE UP TO DATE.ALSO THE TWO FIREFOX INSTALLS CISCO SYSTEMS & WIDEVINE(always active) ALSO UP TO DATE.I NOTICED ONE OTHER THING I FORGOT TO MENTION:

• CLICK ON GEAR
• GET about:preferences#general (OR WHAT EVER TAB YOU CHOOSE TO MAKE CHANGES TO #search...#applications.....#privacy...etc.
• THESE ARE ALSO SHOWN IN THE FIND BAR AS THE ABOVE
• BUT CLICKING ON THE content TAB NOTHING HAPPENS & NOTHING COMES UP IN THE FIND BAR EITHER.

SO I TRIED SOMETHING OUT...

• CLICKED ON GEAR
• GOT THE about:preferences#general
• BACK-SPACED/ERASED general & ENTERED #content
• PRESSED ENTER...NOTHING HAPPENS...PRESSED RELOAD AND I GOT THE SEARCH TAB (options) INSTEAD BUT IT WAS BLANK MEANING IT LISTED ALL OPTIONS BUT NO ENTRIES LIKE LIST OF SEARCH ENGINES AND MT UNCHECKED BOXES.
• SO I DID PRESS THE ACTUAL SEARCH TAB....IT CAME UP ON THE FIND BAR AS about:preferenses#search.....& UP POPS THE ACTUAL TAB WITH ALL MY ENTERED INFO AND ENTRIES I CHOOSE (search engines ,checcked boxes etc)

SO THEIR IS DEFINITELY SOMETHING AMUCK HERE ITS AS IF THE FILE FOR THE CONTENT TAB IS MISSING OR ERASED FROM THE FIREFOX BROWSER.AND WHAT THE HELL HAPPENED TO IT ...CAN YOU SOLVE THIS MYSTERY OR PROBLEM AND FIX IT.WITHOUT DOING ANYTHING TO DRASTIC....MAYBE SOMETHING IN about:config.I NEED TO CHANGE OR FIX.......

You can check for problems with preferences.

Delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

• http://kb.mozillazine.org/preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

I'm having a hard time wrapping my brain around 'clicked on gear' (?)

What happens when you click on the three bar menu => Options => Content  ?

Or when you press Alt, and then (upper left)  : Tools => Options => Content  ?

Nothing  ?

SORRY HAPPY I THOUGHT EVERYONE KNEW THAT THE GEAR ICON WAS FOR THE OPTION PAGE. I GOT CONFUSED WHEN YOU SAID THE THREE BAR MENU..WHEN I JUST REFER IT TO AS THE MENU ICON. WHICH I HAVE EACH ON MY TOOL BAR GEAR UPPER LEFT CORNER AND MENU ICON AT THE FAR RIGHT.ALL I HAVE IN MY (3bar) MENU THE (drop-down) ARE ALL MY ACTIVE EXT..ZOOM BAR..about:firefox(?) ...CUSTOMIZATION BUTTON....& BROWSER KILL BUTTON. NO OPTIONS/CONTENT THEIR AS YOU MENTIONED. AND ALSO I HAVE THE MENU-TOOLS-FILE-EDIT BAR(top left corner) HIDDEN/REMOVED. I LIKE A CLEAN UNCLUTTERED BROWSER SO I HAVE MOST ITEMS HIDDEN.OR I CAN SLIDE THEM OUT WHEN I NEED THEM WITH MY MOUSE.(auto-hide) AS YOU CALL IT. TO YOUR QUESTION IF I CLICK ON ANY WHERE THAT HAS OPTION/CONTENT .....NOTHING STILL HAPPENS

FP45 said

SORRY HAPPY I THOUGHT EVERYONE KNEW THAT THE GEAR ICON WAS FOR THE OPTION PAGE. I GOT CONFUSED WHEN YOU SAID THE THREE BAR MENU..WHEN I JUST REFER IT TO AS THE MENU

Well, that makes two confused people then ..... The 'clicked on gear' confused me, because you have to click on (what I call) the 3-bar menu first (or 'Tools').

I hope cor-el's suggestion will solve this mystery ...... (fingers crossed  !)