To hide the "Sign in to Sync" in the Menu Panel UI (what appears when you click the 3-bar button on the Navigation Toolbar), add this code to a userChrome.css file that you create.

#PanelUI-fxa-status { display: none !important }

http://kb.mozillazine.org/UserChrome.css Note, you 'll also need to create the chrome folder for that file, too.

Thanks for the reply. However that particular setting does not speak to the setting I'm referring to above. To confirm, the sync menu/button I'm referring to is under options.

Whoops, sorry about that. My answer was for the Sync menu item in the Menu Panel that appears when clicking the 3-bar "Open menu" button which is on the Navigation Toolbar. That is the "sync" item that most people ask about hiding; coupled with your mention of userChrome code -- that generated a "mind fart" here. ;>P

This is the code to hide the Sync tab in the about:preferences tab for "Options".

Note - this is not userChrome.css code, but rather userContent.css code.

 @-moz-document url("about:preferences") {
#category-sync { display:none!important; }
} 

http://kb.mozillazine.org/UserContent.css

Hide Sync in Menu 0.9.3 No Restart by Aleksandr Seleznev https://addons.mozilla.org/en-US/firefox/addon/hide-sync-in-menu Hide "Sign in to Sync" button in the menu.

^ Fred, that add-on doesn't look like it does anything more than the first userChrome.css script that I posted on the 10th. It sure as hell doesn't hide the Options / Preferences tab that this user asked about, nor it does it hide the Synced Tabs button that is sitting in Customize > Additional Tools and Features.

the-edmeister said

Whoops, sorry about that. My answer was for the Sync menu item in the Menu Panel that appears when clicking the 3-bar "Open menu" button which is on the Navigation Toolbar. That is the "sync" item that most people ask about hiding; coupled with your mention of userChrome code -- that generated a "mind fart" here. ;>P

---

This is the code to hide the Sync tab in the about:preferences tab for "Options".

Note - this is not userChrome.css code, but rather userContent.css code.

 @-moz-document url("about:preferences") {
#category-sync { display:none!important; }
} 

http://kb.mozillazine.org/UserContent.css

Thanks again for the response . Once more I'm on my mobile device so my response will be short; please don't misconstrue for being curt! :) This looks promising so thank you kindly. Will test next week. Also appreciate the correction on the .CSS file.

Just curious, how does one go about figuring this out? Is this documented somewhere or does one have to look at some .h file somewhere and hope. Would like to get a better understanding of Firefox's configuration nuances.

Just curious, how does one go about figuring this out?

I pick it up here and there.

There's a lot of good User Styles over here - https://userstyles.org/ - which are made by users to work with the Stylish extension. Some styles that I use I put into Stylish, but sometimes I 'grab' a line or two of code from a User Style or two and put it in a userChrome.css or userContent.css file if its something that I want in all my Firefox Profiles. Saves me a lot of time when I want to create a new Profile; especially when it comes to a user.js file to set my preferences in one file rather than root around about:config making a couple dozen changes and trying to remember all those changes. I even set a few prefs that are particular to extensions that I commonly use.

I tend to use Stylish when it comes to customizing for just a single Profile.

the-edmeister said

This is the code to hide the Sync tab in the about:preferences tab for "Options". Note - this is not userChrome.css code, but rather userContent.css code.

 @-moz-document url("about:preferences") {
#category-sync { display:none!important; }
} 

http://kb.mozillazine.org/UserContent.css

Winner winner chicken dinner. Thanks for this!