function checkform(form){
  var emailreg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
  var name = form.contact_name.value;
  var email = form.contact_email.value;
  var subject = form.contact_subject.value;
  var message = form.contact_message.value;
  var security_code = form.security_code.value;
  var captcha_result = document.getElementById('captcha_result').value;
  
  if(name == '' || email == '' || subject == '' || message == '' ){
    alert('All Fields are Required.');
    return false;
  }else if(emailreg.test(email) == false) {
    alert('Please check your email address.');
    return false;
  }else if (captcha_result != 'valid'){
    alert('Please type the security code.');
    return false;
  }else{
    thankyou();
    return true;
  }
  return false;
}

function thankyou(){
  newwindow=window.open('thankyou.php','name','height=200,width=400');
	if (window.focus) {newwindow.focus()}
}