01 - changing the background color
So I wrote a little script to change the background color of the whole document, which turned out not to work because the background color is defined in the CSS file, not the HTML. So I had to revamp it a little and make it just change the background of this inner window.

Try it out for yourself!

Change the whindow's background color to:
medium-ish grey
light blue
original blue
same as body

Well, that's about as exciting as it gets folks ...

p.s. If you're using a browser that doesn's support the "document.getElementById" method, this won't work at all.