Kim587: I find putting the cursor down in the bottom left corner gets rid of the ribbon at the bottom.
I'm sure I tried that and a host of Esc keys, right clicking all over the screen etc. Only way I was able to get rid of it for sure was to close it down and open the same game in a new window. I was using IE on my kid's laptop. I can't recall when I was testing this before on my gaming PC using Firefox whether I had the same problem then. Will trial again when I get home.