msieCheck.js

/**
 * Test for IE
 *   - http://blogs.msdn.com/giorgio/archive/2009/04/14/how-to-detect-ie8-using-javascript-client-side.aspx
 *   - http://blogs.msdn.com/mikeormond/archive/2008/09/25/ie-8-compatibility-meta-tags-http-headers-user-agent-strings-etc-etc.aspx
 *   - http://msdn.microsoft.com/en-gb/library/cc817572.aspx
 *   - http://stackoverflow.com/questions/5825385/javascript-can-i-detect-ie9-if-its-in-ie7-or-ie8-compatibility-mode
 */
if(window.ActiveXObject){
	var rv = -1;
	var ua = navigator.userAgent;
	var re = new RegExp("Trident\/([0-9]{1,}[\.0-9]{0,})");
	if (re.test(ua)) {
		rv = parseFloat(RegExp.$1);
	}  
	var msie9 = (rv == 5) || ("performance" in window);
	var msie8 = (rv == 4) && !msie9;
	var msie7 = window.XMLHttpRequest && !(msie8 || msie9); 
	// var msie6 = (!!(window.attachEvent && navigator.userAgent.indexOf('Opera') === -1)) && /MSIE 6/i.test(navigator.userAgent);
	// var msie6 = !(msie7 || msie8 || msie9);
}