Internet Explorer iconfont problems

Question

I have a little problems with icon webfont and IE. With Chrome, the font-size:1.3em is correctly displayed. But with IE, the font-size isn't respected (in px and in em...).

I have tested a font-size in em and px.

https://i.stack.imgur.com/RtV84.png

[class^="flaticon-"]:before, [class*=" flaticon-"]:before, [class^="flaticon-"]:after, [class*=" flaticon-"]:after {
  font-family: Flaticon;
  font-size: 30px;
  font-style: normal;
  margin-right: 10px;
  vertical-align: middle;
}

the header.php's file where are the icons : http://pastebin.com/4kcTy5ew

Thanks for your help !