function check_version() {
 	var app=navigator.appName;
 	var version=navigator.appVersion;
 
 	var ver="explorer";
	  if (app.indexOf('Netscape')!=-1) {
   		ver="netscape";
  	}
  	if (app.indexOf('Microsoft')!=-1) {
   		var version_num=parseFloat(version);
    if (version_num<4) {
      ver="netscape";
    }
  }
 return ver;
}