fixed 'unknow runtime error' ie IE8

Author: wisely0515

lib/helpers/injectCSS.js

@@ -34,9 +34,15 @@ function injectStyle(css) {
   if (!style) {
     style = document.createElement('style');
     style.setAttribute('id', 'rackt-style');
-    var head = document.getElementsByTagName('head')[0];
-    head.insertBefore(style, head.firstChild);
+    style.setAttribute("type", "text/css");
+  }
+
+  if (style.styleSheet) {
+    style.styleSheet.cssText = css;
+    document.body.appendChild(style);
+  } else {
+    style.innerHTML = css;
+    document.head.appendChild(style);
   }
-  style.innerHTML = style.innerHTML+'\n'+css;
 }