I think that preference refers to what happens when you have Firefox maximized and you do not display either the classic menu bar or the title of the page in that area: the tabs slide up to the top.

I agree the double-high blue area is irritating. To modify that, I think you need to do one of these:

• Change the Windows XP color theme (I always preferred Silver)
• Create a custom style rule to modify the appearance of the tab bar (so the blue does not show through it)
• Find a Firefox theme that fixes that area (e.g., https://addons.mozilla.org/firefox/themes/)

I haven't researched the second and third options in detail.

By the way, I think the local-settings.js file generally points to a mozilla.cfg file. Maybe that will work?

http://kb.mozillazine.org/Locking_preferences

You would have to use this content in the mozilla.cfg file.

//
lockPref("browser.tabs.drawInTitlebar", false);

These functions can be used in the mozilla.cfg file:

defaultPref();	// set new default value
pref();		// set pref, but allow changes in current session
lockPref();	// lock pref, disallow changes

See also:

• http://mike.kaply.com/2012/03/16/customizing-firefox-autoconfig-files/

Thanks to all. Problem solved. I should edit 2 files:

C:\Program Files\Mozilla Firefox\defaults\pref\local-settings.js pref("general.config.obscure_value", 0); pref("general.config.filename", "mozilla.cfg");

C:\Program Files\Mozilla Firefox\mozilla.cfg // lockPref("browser.tabs.drawInTitlebar", false);