ajax issue, code from form isn't executed

The form, it's because of the table? Or what's the problem that causes the data to not send? I added a function onClick.... but doesn't work .
Maybe someone has a sollution for this problem.

Btw, the html is not complete, all the id's & names are existent.
The html page

<script src="js/ajax_register.js" type="text/javascript"></script> 
<form name="form1" id="form1"><table border="0" id="table_box">
    <tr><td width="81">Username:</td><td width="146"><input type="text" name="username" class="textfield" id="username"/></td></tr>
    <tr><td>Password:</td> <td><input type="password" name="password" class="textfield" id="password"/></td></tr>
    <tr><td>Email:</td> <td><input type="text" name="email" class="textfield" id="email"/></td></tr>
    <tr><td>Full Name:</td> <td><input type="text" name="name" class="textfield" id="name"/></td></tr>
    
    <tr><td></td><td align="right"><a href='#' id="bolded" onClick="showResult()">Create Account</a></td></tr>
    </table>
</form>

PHP:

The ajax_register.js page

var xmlHttp
function showResult(){
var str=document.getElementsById("username").value;
var password=document.getElementsById("password").value;
var email=document.getElementsById("email").value;
var name=document.getElementsById("name").value;
if(str.length==0){ 
 document.getElementById("result").innerHTML="";
 document.getElementById("result").style.border="0px";
 document.write("you forgot to complete all the fields");
 return
 }
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null){
 return
 } 
var url="data.php"
url=url+"?usr="+str
url=url+"&cod="+password
url=url+"&email="+email
url=url+"&name="+name
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged 
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
} 
function stateChanged(){ 
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
 { 
 document.getElementById("result").innerHTML=xmlHttp.responseText;
 document.getElementById("form1").style.display="none";
 }
else{
 document.getElementById("lic").style.display="none";
}
}

function GetXmlHttpObject()
{
var xmlHttp=null;
try{
 xmlHttp=new XMLHttpRequest();
 }
catch (e){
 try
  {
  xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  }
 catch (e)
  {
  xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
 }
return xmlHttp;
}

PHP:

[Solved]the main problem was the document.getElementsById