var agent = navigator.userAgent.toLowerCase();
var win = (agent.indexOf("windows") != -1);
var mac = (agent.indexOf("mac") != -1);
var opera = agent.indexOf("opera",0) != -1;
var ie = agent.indexOf("msie") != -1 && !opera;
var ie45 = agent.indexOf("msie 4.5") != -1;
var ns = agent.indexOf("netscape") != -1 && !opera;
var plugin;