function checkContactForm()
{
  if(document.getElementById('i_am_interested_in').value == '')
  {
    alert('Please choose the subject of this inquiry.');
    return false;
  }
  if(document.getElementById('contact_name').value == '')
  {
    alert('Please enter your name.');
    document.getElementById('contact_name').select();
    return false;
  }
  if(document.getElementById('phone_number').value == '')
  {
    alert('Please enter your phone number.');
    document.getElementById('phone_number').select();
    return false;
  }
  if(document.getElementById('email_address').value == '')
  {
    alert('Please enter your email address.');
    document.getElementById('email_address').select();
    return false;
  }
  if(document.getElementById('comments').value == '')
  {
    alert('Please enter some comments.');
    document.getElementById('comments').select();
    return false;
  }
  return true;
}