I personally like being able to close each tab individually in Firefox but if you get too clicky happy you can close tabs by mistake which can be a pain. Here's a little trick to remove the x's from each tab which makes it impossible to close a tab in error again.

Type about:config in the address bar. You will see the message (if you're doing this for the first time) "I'll be careful I promise", click on it.

Scroll to brower.tabs.closeButtons, double click on it and in the Enter integer value box

Enter 0 = Firefox will display a close button only on the tab that you're currently on.

Enter 2 = Firefox will not display a close button on any tab

If you want to change it back just do the process over again and type 1 back in.

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