function checkContactForm()
{
  if(document.getElementById('first_name').value == '')
  {
    alert('Please enter your first name.');
    document.getElementById('first_name').select();
    return false;
  }
  if(document.getElementById('last_name').value == '')
  {
    alert('Please enter your last name.');
    document.getElementById('last_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('best_time_to_call').value == '')
  {
    alert('Please enter the best time to call.');
    document.getElementById('best_time_to_call').select();
    return false;
  }
  if(!document.getElementById('new_patient-1').checked  &&  !document.getElementById('new_patient-2').checked)
  {
    alert('Please indicate whether or not you are a new patient.');
    return false;
  }
  if(document.getElementById('appointment_month').value == '')
  {
    alert('Please choose the month you\'d like to schedule your appointment for.');
    return false;
  }
  if(document.getElementById('appointment_day').value == '')
  {
    alert('Please choose the day of the month you\'d like to schedule your appointment for.');
    return false;
  }
  if(document.getElementById('appointment_year').value == '')
  {
    alert('Please choose the year you\'d like to schedule your appointment for.');
    return false;
  }
  if(document.getElementById('preferred_day').value == '')
  {
    alert('Please choose the day of the week you prefer.');
    return false;
  }
  if(document.getElementById('which_is_more_flexible').value == '')
  {
    alert('Please choose which is more flexible for you.');
    return false;
  }
  return true;
}