function checkForm() {
  firstname = document.getElementById("firstname").value;
  lastname = document.getElementById("lastname").value;
  email = document.getElementById("email").value;
  
  hideAllErrors();
  error = false;

  if (firstname == "") {
    document.getElementById("firstnameError").style.display = "block";
    error = true;
  }
  
  if (lastname == "") {
    document.getElementById("lastnameError").style.display = "block";
    error = true;
  }
  
  if (email == "") {
    document.getElementById("emailError").style.display = "block";
    error = true;
  }
  
  if(error == true) {
    return false;
  }
  else {
	return true;  
  }
}
 
function hideAllErrors() {
  document.getElementById("firstnameError").style.display = "none"
  document.getElementById("lastnameError").style.display = "none"
  document.getElementById("emailError").style.display = "none"
}