app = navigator.appName.charAt(0);
    ver = navigator.appVersion.charAt(0);
    var cssDir = 'topics/css/';
    var cssTags = '<link rel="stylesheet" type="text/css" href="';
    var flag = null;
    if(navigator.userAgent.indexOf("Mac")!=-1){
    if (app == "N") {   
		flag = "mns";
		document.open();
		document.write(cssTags + cssDir + flag + '.css" title="MacNS_style">');
		document.close();
       } else {   
		flag = "mie";
		document.open();
		document.write(cssTags + cssDir + flag + '.css" title="MacIE_style">');
		document.close();
       } 
    } else {
    if (app == "N") {   
		flag = "wns";
		document.open();
		document.write(cssTags + cssDir + flag + '.css" title="WinNS_style">');
		document.close();
       } else {   
		flag = "wie";
		document.open();
		document.write(cssTags + cssDir + flag + '.css" title="WinIE_style">');
		document.close();
       } 

       }