try clicking on the left edge of the green bar

sorry if it's not intuitive - I wanted the content to not be too wide (for reading) and had an idea to place some non-critical things on the remaining space, but then I decided it shouldn't always be visible

edit: I've fixed the page to make the green tab visible by default

The best way to cue that it is clickable is to have it "bounce" when you mouse over it, indicating that it is hidden on purpose and can be expanded.

Thanks, I've seen those bounces before but it never occurred to me to use it.

btw, I love your blog

Same. Firefox Win7

I usually don't interrupt my reading so often with interaction. I like to read a section at a time and then do the exercises. But with this format, I could see dabbling in a little interactive work more often - which is probably a good thing.

same with safari, osx