This page requests IE9 mode using <meta http-equiv="X-UA-Compatible" content="IE=9">
. document.documentMode
says: .
There are three ways to rotate a square 45° below.
-ms-transform: rotate(45deg);
Supported by IE9 and the IE9 mode in IE10.
transform: rotate(45deg);
Not supported by the real IE9 but supported by the IE9 mode in IE10. Oops!
transform: rotateZ(45deg);
Supported by the IE10 mode. Consistently not supported by either the real IE9 or the IE9 mode in IE10.