function checkData()
{
  var validname = true;
  var validphone = true;
  var validemail = true;
  var validzip = true;

  var name = document.landing1.name.value;
  var phone = document.landing1.phone.value;
  var email = document.landing1.email.value;
  var zipcode = document.landing1.zipcode.value;

  if(/^\s*$/.test(name))
    validname = false;

  if(!/([ ]*\([ ]*\d{3}[ ]*\)[ ]*|\d{3}([ ]*-?[ ]*))\d{3}([ ]*|[ ]*-[ ]*)\d{4}/.test(phone))
    validphone = false;

  if(!/[a-z0-9]+([_\.\-+][a-z0-9]+)*@[a-z0-9]+([_\.\-+][a-z0-9]+)*\.[a-z]{2,4}/.test(email.toLowerCase()))
    validemail = false;

  if(!/\d{5}/.test(zipcode))
    validzip = false;

  if(validname && validphone && validemail && validzip)
  {
    alert('Thank you for your support! Your information has been submitted.');
    return true;
  }

  var ret = 'The following fields are missing or incorrectly filled out:\n';
  if(!validname)
    ret += '  * Name\n';
  if(!validphone)
    ret += '  * Phone number\n';
  if(!validemail)
    ret += '  * Email\n';
  if(!validzip)
    ret += '  * Zip code\n';
  ret += 'Please correct these fields and click \"Join the campaign\" again.'
  alert(ret);

  return false;
}