After installing Firefox it placed a symbol in the taskbar from which to launch it. When moving the mouse above this symbol it would then also display the various tabs that were open in the browser. So, the program was launched from and operating inside this ONE Firefox symbol on the taskbar... there was never (at any given point), more than one symbol.

Now suddenly it started opening a second Firefox symbol in the taskbar in which the browser actually runs and displays the open tabs. In other words I now have one Firefox symbol in the taskbar to launch the browser, and another, second symbol in which the browser runs. I don't want this because it takes up too much space on the taskbar. How can I get back to keeping Firefox limited to one symbol on the taskbar at all times?