Why do I get a message "CCLI is an experiment..."

[joneall]

When I log on, there is a lone black box with this in it:

CCLI is an experiment to create a highly usable command line for web developers. For a list of commands type >>help, or to show/hide command hints press F1/Escape.

Then there is a button which says "Got it!".

What does this mean but, mainly, why am I getting it?

[ronw]

You probably hit the shortcut key, Shift+F2, while the browser had focus. It's a Mozilla/Firefox developer tool.

[joneall]

You probably hit the shortcut key, Shift+F2, while the browser had focus. It's a Mozilla/Firefox developer tool.

I don't think it's that because I tried it with the browser and nothing happened.