if (document.layers){ //Netscape 4.x
document.write("<LINK REL='stylesheet' HREF='css/nn.css' TYPE='text/css'>");
}
else if (document.all){ // Explorer
document.write("<LINK REL='stylesheet' HREF='css/ie.css' TYPE='text/css'>");
}
else if (document.getElementById){ //Netscape 6.x
document.write("<LINK REL='stylesheet' HREF='css/n6.css' TYPE='text/css'>");
}