if(navigator.appVersion.indexOf("Mac",0) != -1){
//?os
if(navigator.userAgent.indexOf("Netscape6/6.0",0) != -1){
//mac ns6
document.writeln("");
}
else if(navigator.appVersion.indexOf("MSIE 5.0")<=0){
//mac ns
document.writeln("");
}
else{
//mac ie5
document.writeln("");
}
}else {
//win
document.writeln("");
}