IE browser detect, including ie version, and ie document mode.

ie_browser_detect

var ua = navigator.userAgent;
  var isIE = ua.indexOf("MSIE") != -1;
	var ieVersion;
	var mode = document.documentMode ||
	((/back/i).test(document.compatMode || "") ? 5 : ieVersion) ||
	((/MSIE\s*(\d+\.?\d*)/i).test(navigator.userAgent || "") ? parseFloat(RegExp.$1, 10) : null);
	function getIEVersion(dataString) {
		var index = dataString.indexOf("MSIE");
		if (index == -1) return;
		return parseFloat(dataString.substring(index+5));
	}
	if(isIE) {
		ieVersion = getIEVersion(navigator.userAgent);
		//alert('version '+ ieVersion);
		if(ieVersion < 10) {
			//alert('document.documentMode ' + document.documentMode);
			if(mode < 7 || !mode) {
				//do something here, example
				return;
			}
		}
	}