// convert all characters to lowercase to simplify testing
    var agt=navigator.userAgent.toLowerCase();
    
	var is_mac    = (agt.indexOf("mac")!=-1);
    
if (is_mac) {

   document.write("<LINK REL=stylesheet HREF=\"survey_mac.css\" TYPE=\"text/css\">"); }

else {

   document.write("<LINK REL=stylesheet HREF=\"survey.css\" TYPE=\"text/css\">"); }