I have just updated my operating system to Debian "Stretch" and installed Mozilla Firefox browser.
I experienced some problems with the browser on the previous version of the operating system. Internet links in messengers and LibreOffice did not open in an opened instance of the browser but a new browser window always appeared with the home page opened. So, I had to manually copy links to the browser. Another problem was with the Gnome side panel. I had to manually create a launcher for the browser using Main Menu program and then move the new launcher to the side panel. Such a link worked but not in an expected way. When I clicked on the Mozilla Firefox link on the side panel, a new link appeared there and two labels for the browser were there. But the idea of a link on the side panel is just to highlight a clicked label to save space.
I am eager to say that the configuration that I use now allows solving this two, not serious but anyway, unpleasant problems.