var isOpera = (typeof(window.opera) != "undefined");
var isIE = (navigator.userAgent.indexOf("MSIE") != -1) && !window.opera;
var isIE7 = (navigator.userAgent.indexOf("MSIE 7") != -1) && !window.opera && (typeof(XMLHttpRequest) != "undefined");
var isGecko = ((navigator.userAgent.indexOf("Gecko") != -1) && (navigator.appVersion.indexOf("AppleWebKit") == -1));
var isSafari = (navigator.appVersion.indexOf("AppleWebKit") != -1);

document.documentElement.className += " " + (isIE7?"ie7":(isIE?"ie":(isGecko?"gecko":(isOpera?"opera":(isSafari?"safari":"unknown")))));