$(document).ready(function(){

 var txtEmailAddress = $('#txtEmailAddress');
 var messageDiv = $('#MessageDiv');
 $('#btnSubmit').click(function(e)
 {

 txtEmailAddressValue = txtEmailAddress.val();

 if (txtEmailAddressValue == '')
 {
 messageDiv.html('<p>Email address required</p>');
 messageDiv.fadeIn(400);
 
 txtEmailAddress.focus();
 
 return false;

 }
 else
 {
 
 if (!IsValidEmail(txtEmailAddressValue))
 {
 messageDiv.html('<p>Please enter a valid email!</p>');
 messageDiv.fadeIn(400);
 
 txtEmailAddress.focus();
 
 return false;
 }
 else
 {
 messageDiv.html('');
 messageDiv.hide();
 
  return true;
 }
 }
 });

 function IsValidEmail(email)
 {
 var filter = /^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;
 return filter.test(email);
 } 
 });