var agt = navigator.userAgent.toLowerCase()
var appVer = navigator.appVersion.toLowerCase()

var is_win = ( (agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1) )
var is_mac = (agt.indexOf("mac")!=-1)

var iePos = appVer.indexOf('msie')
var is_ie = ((iePos!=-1))