Some members reported that, when browsing the forum with their mobile, an annoying black bar appears on the screen showing [home] in the middle.

I couldn't replicate it until I installed Firefox for testing (members reporting this have FF installed), then it also appeared on my screen.

Is Firefox not compatible with the IPS software?

Also, when I'm using the Slimperience browser, my screen goes partly outside of my mobile screen, on the right side.

Which browser, (excepted Google Chrome!) do you advice using?

Member's screen:

My screen:

 

You have this installed...

 

As Nathan mentioned, this is not something which is in our software but is the add-on mentioned (or something else). I would advise disabling all third party add-ons and switching to a non-modified theme to test. 

Plugin disabled and the black bar is gone.

Thank you so much to both of you, for your kind and quick response.

Your replies brought the solution to this problem I was having. 💖👍