var xmlhttp;

         function check_user_name(element,str){
                  
                  
                  
                  if(str.length>=3){
                  
         
                                    xmlhttp=GetXmlHttpObject();
                                   
                                    if(xmlhttp==null){
                                             
                                             alert ("Browser does not support HTTP Request");
                                             return;
                                    }
                                      
                                    var url="check_user.php";
                                    
                                    url=url+"?q="+str;
                                    
                                    url=url+"&sid="+Math.random();
                                    
                                    xmlhttp.onreadystatechange=stateChanged;
                                    
                                    xmlhttp.open("GET",url,true);
                                    
                                    xmlhttp.send(null);
                  }                  
         
         }

         function stateChanged(){

                  if (xmlhttp.readyState==4){
                           
                           var user_name_exist=xmlhttp.responseText;
                           
                           if(user_name_exist==1){
                                    
                                    
                                    document.getElementById("reg_email").focus();
                                    document.getElementById("user_name_message").innerHTML='<font class=off>Existing user name</font>';
                                    document.getElementById("user_name_avail").value=false;
                           }else{
                                    
                                    document.getElementById("user_name_message").innerHTML='<font class=on>User name available</font>';
                                    document.getElementById("user_name_avail").value=true;
                           }
                  
                           
                  }
         }


         function GetXmlHttpObject(){
                  
                  if (window.XMLHttpRequest){
                           
                           // code for IE7+, Firefox, Chrome, Opera, Safari
                           return new XMLHttpRequest();
                  }
                  
         
                  if (window.ActiveXObject){
                           
                    // code for IE6, IE5
                    return new ActiveXObject("Microsoft.XMLHTTP");
                  }
                  
                  return null;
         }