


You can use this button to go to the currently used Firefox profile folder: The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session. You can check its content with a plain text editor (right-click: Open with) if you didn't create this file yourself. The user.js file is only present if you or other software has created this file and normally it wouldn't be there. Note that your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. If you mean the Most Visited item on the Bookmarks Toolbar then you can reset the pref via the right-click context menu to 0 and close and restart Firefox. Your System Details list doesn't show a modified pref, so if you are talking about the about:newtab page then check if you see a grid icon in the top right corner to enable to new tab page.

