Ajax no refresh

var xmlHttp; 
uName() //When the username loses focus & NBSP;
{ 
 if(all.uname.=="") 
 { 
  all.l1.innerHTML=" Can't be empty! "; 
  setTimeout("close(1)",1500); 
  return; 
 } 
 else 
 { 
  xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); 
  xmlHttp.onreadystatechange=deal; //Callback function & NBSP;
  var url="aJax.aspx?user='"+all.uname.+"'"; //You will jump to the page that detects the username & NBSP;
  xmlHttp.open("get",url,true); //Submit the form to the url in get mode; And start a one-step process & NBSP;
  xmlHttp.send(null); //Send  
 } 
} 
deal() 
{ 
 //alert(xmlHttp.readystate+"__"+xmlHttp.status); 
 if(xmlHttp.readystate!=4) 
 {return; } 
 if(xmlHttp.status!=200)  //Equals 500 is an SQL statement or database error & NBSP;
 {return;} 
 // 
 var num = xmlHttp.responseText; //Receive the message sent by the server & NBSP;
 //alert(num); 
 all.l1.innerText=""; 
 if(num>0) 
 { 
  all.l1.innerText=" The secondary username has been used! "; 
 } 
 else  
 { 
  all.l1.innerText=" Square root "; 
 } 
}