Type '''about:addons'''<enter> in the address bar to open the Add-ons Manager. Hot key; '''<Control> ''(Mac=<Command>)'' <Shift> A)''' On the left side of the page, select '''Appearance. ''' Then select '''Default. ''' Now restart Firefox. -------------- '''Separate Security Issue:''' Update your Flash Player or remove it using these links; http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html Uninstall Flash Player | Windows http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html Uninstall Flash Player | Mac '''Note: Windows users''' should download the '''ActiveX''' for ''Internet Explorer.'' '''and''' the '''plugin''' for ''Plugin-based browsers'' (like Firefox). '''Note: Windows 8 and Windows 10''' have built-in flash players and Adobe will cause a conflict. Install the plugin only. Not the ActiveX. Flash Player Version: '''Version 31.0.0.148 ''' https://get.adobe.com/flashplayer/ Direct link scans current system and browser '''Note: Other software''' is offered in the download. <Windows Only> https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) '''Note: Other software''' is offered in the download. <Windows Only> +++++++++++++++++++ See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

firefox will always have a standard theme installed to run it's browser so what is the issue with the themes?

// first line is a comment line
lockPref("lightweightThemes.usedThemes","[]");
lockPref("lightweightThemes.selectedThemeID", "default-theme@mozilla.org");

Try to lock some theme prefs via an autoconfig.cfg file. *https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig ---- <pre><nowiki>// first line is a comment line lockPref("lightweightThemes.usedThemes","[]"); lockPref("lightweightThemes.selectedThemeID", "default-theme@mozilla.org"); </nowiki></pre>

Hi cor-el, It seems a good idea. I test it. Thanks.

Hi cor-el, Thank you very much ! It works great.