This week's "Keyboard Shortcut of the Week" gets 10 out of 10 in
the categories "Obscurity", "Wackiness", and "Hmmm. Not wild about
it, but pretty cool anyway."
So, you're in the source view of something that also has a
design view. Which, basically, means you're in the source view of
the Matisse GUI Builder. Or, possibly, you're in the source view of
the web.xml Visual Editor. (Or, I guess, you could even be in the
source view of your own MultiView API implementation.) Or...