function linkCSS(layerNo) {
	var usra = navigator.userAgent;
	var osMac = (usra.indexOf("Mac") != -1)?true:false;

	if (layerNo == 1)  { dirName = "./";}
	if (layerNo == 2)  { dirName = "../";}
	if (layerNo == 3)  { dirName = "../../";}
	if (layerNo == 4)  { dirName = "../../../";}

	if(osMac){
		cssName = "css/mac.css";	// mac
	}else{
		cssName = "css/win.css";	// win,other
	}

	document.write('<link rel=\"stylesheet\" href=\"' + dirName + cssName +'\" type=\"text/css\">');
	document.write('<link rel=\"stylesheet\" href=\"' + dirName + 'css/common.css\" type=\"text/css\">');
}