This is the way to be absolutely certain :
<!doctype html> <!-- html5 -->
<html lang="en"> <!-- lang="xx" is allowed, but NO xmlns="http://www.w3.org/1999/xhtml", lang:xml="", and so on -->
<head>
<meta http-equiv="x-ua-compatible" content="IE=Edge"/>
<!-- as the **very** first line just after head-->
..
</head>
Reason :
Whenever IE meets anything that conflicts, it turns back to "IE 7 standards mode", ignoring the x-ua-compatible
.
(I know this is an answer to a very old question, but I have struggled with this myself, and above scheme is the correct answer. It works all the way, everytime)