window.onload = initPage;

function initPage() {
  document.getElementById("username").onblur = checkUsername;
  document.getElementById("register").disabled = true;
}

function checkUsername() {
  document.getElementById("username").className = "thinking";
  request = createRequest();
  if (request == null)
    alert("Unable to create request");
  else {
    var theName = document.getElementById("username").value;
    var username = escape(theName);
    var url= "submit.aspx?username=" + username;
    request.onreadystatechange = showUsernameStatus;
    request.open("GET", url, true);
    request.send(null);
  }
}