function close(){

var userAgent = navigator.userAgent;
if (userAgent.indexOf("Firefox") != -1 || userAgent.indexOf("Chrome") !=-1) {
  window.location.href="about:blank";
}else if(userAgent.indexOf('Android') > -1 || userAgent.indexOf('Linux') > -1){
  window.opener=null;window.open('about:blank','_self','').close();
}else {
  window.opener = null;
  window.open("about:blank", "_self");
  window.close();
}