var setFocus = function() {
 document.getElementById("email_addr").focus();
};

var checkEmail = function() {
 if(!document.getElementById("email_addr").value) {
  setFocus();
  return false;
 }
};

var flashDot = function() {

 var dot = document.getElementById("dot");
 var show = true;

 var flip = function() {

  if (show == false) {
   dot.style.visibility = "hidden";
   show = true;
  } else {
   dot.style.visibility = "visible";
   show = false;
  }

  setTimeout(flip, 1000);
 };
 flip();
};

window.onload = function() { 
 document.getElementsByTagName("form")[0].onsubmit=checkEmail;
 flashDot();
 setFocus();
};