In this doc, we are using the following as our meta tag:

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9" >

See the index page for notes on efficacy and other tests.

And now, some tests:

What IE mode am I rendering in (based on html Conditional Comments)?

Capabilities tests using CSS:

Reliable Javascript test that uses both CC html and CC javascript:

No version of IE passes the X-UA-Compatible meta value to a child iframe without one.