Hello. IE 9 has weird thing with border radiuses. Lets take a example:
border-radius: 10px;
It will not work in IE 9. Now you ask why, because it IS supported in IE 9. Well the problem is in common syntax mistake. The working code should look like this:
border-radius: 10px 10px 10px 10px;
IE 9 needs full values for border radius! I can't memorize where did I read that, but it was on a IE article, somewhere And don't forget this:
<meta http-equiv="X-UA-Compatible" content="IE=edge" />