function validNewUserEntries(form) {

  var userName = form.userName.value;
  var password = form.password.value;
  var password2 = form.password2.value;
  var firstName = form.firstName.value;
  var lastName = form.lastName.value;
  var emailAddress = form.emailAddress.value;
  var yearOfBirth = form.yearOfBirth.value;
  var zipCode = form.zipCode.value;

  if(userName == "") {
    alert("You must enter a user name.");
    form.userName.focus();
    return false;
  }
  if(password == "" || password2 == "") {
    alert("You must enter the same password in both password fields.");
    form.password.value = "";
    form.password2.value = "";
    form.password.focus();
    return false;
  }
  if(password != password2) {
    alert("You have not entered the same password in both password fields, please re-enter your password.");
    form.password.value = "";
    form.password2.value = "";
    form.password.focus();
    return false;
  }
  var passwordRegex = /^[a-zA-Z0-9]+$/;
  if(!passwordRegex.test(password)){
    alert("The password you entered is invalid. Please enter a valid password.");
    form.password.value = "";
    form.password2.value = "";
    form.password.focus();
    return false;
  }  
  if(firstName == "") {
    alert("You must enter your first name.");
    form.firstName.focus();
    return false;
  }
  if(lastName == "") {
    alert("You must enter your last name.");
    form.lastName.focus();
    return false;
  }
  if(emailAddress == "") {
    alert("You must enter your email address.");
    form.emailAddress.focus();
    return false;
  }
  var emailRegex = /^[a-zA-Z0-9._-]+@([a-zA-Z0-9.-]+\.)+[a-zA-Z0-9.-]{2,4}$/;
  if(!emailRegex.test(emailAddress)){
    alert("The email you entered is invalid. Please enter a valid email address.");
    form.emailAddress.value = "";
    form.emailAddress.focus();
    return false;
  }
  if(!(yearOfBirth > 1900 && yearOfBirth < 2010) && yearOfBirth != ""){
    alert("Please enter your YEAR of birth, not your date of birth. For example 1978. Alternatively you may leave the field blank.");
    form.yearOfBirth.value = "";
    form.yearOfBirth.focus();
    return false;
  }    
  if((zipCode != "") && (form.zipCode.value.length != 5)){
    alert("You have entered an invalid zip code. Please enter a valid zip code or leave the field blank.");
    form.zipCode.value = "";
    form.zipCode.focus();
    return false;
  }    
  return true;
}