Different keyboard layouts. The big difference between UK and US layouts tends to be swapping the " and @ symbols, so on a UK keyboard the ! is shift+1 and the " is shift+2.

I never had that floating over the document I was viewing, just in the home tab of the menu, but I did find a way to switch it off. ‘File > Preferences > General’ has an option to ‘disable all features which require an internet connection’. There are also options in there to disable that opening splash screen if you don’t want that.