browser	 = (navigator.appName.toLowerCase().indexOf("netscape") >= 0) ? "ns" : "ie";
platform = (navigator.platform.toLowerCase().indexOf("mac") >= 0) ? "mac" : "pc";
platformStyle = (browser == "ie") ? "" : ("_" + platform);

document.write('<Link Type="text/css" Rel="stylesheet" href="css/styles_' + browser + platformStyle + '.css">');

// TEST :

//alert("css_" + browser + platformStyle + ".css");

// RESULT:
 
//href="styles_ns_mac.css";
//href="styles_ns_pc.css";
//href="styles_ie.css";

//alert("Hello");