if(navigator.appName=="Microsoft Internet Explorer" && navigator.platform=="Win32"){
document.write('<LINK rel="stylesheet" type="text/css" href="default1.css">');
}
if(navigator.appName=="Netscape" && navigator.platform=="Win32"){
document.write('<LINK rel="stylesheet" type="text/css" href="default1.css">');
}
if(navigator.appName=="Microsoft Internet Explorer" && navigator.platform=="MacPPC"){
document.write('<LINK rel="stylesheet" type="text/css" href="default2.css">');
}
if(navigator.appName=="Netscape" && navigator.platform=="MacPPC"){
document.write('<LINK rel="stylesheet" type="text/css" href="default3.css">');
}