What did you learn today? Owt or nowt?

Maybe its age, but days seem to slip past too fast. So, a resolution; try to learn or experience one new techy thing every day and post it here.

Today's new thing : cross-domain client side web integration : use postMessage(). It has limitations (especially on IE : thanks microsoft) but does the job in a world of iframes...

Go here for info on the problem:
http://en.wikipedia.org/wiki/Same_origin_policy

Here's a good article explaining the use:
http://72lions.com/2011/05/cross-origin-communication-with-html5

and here's the browser support matrix:

http://caniuse.com/x-doc-messaging