function validate_form()
{
  var missing = "";
  valid = true;

  if (document.info_request.realname.value == "") {
    missing = "Name";
    document.info_request.realname.focus();
    valid = false;
  }
  if (document.info_request.tel.value == "") {
    if (valid == false) missing += ", "
    missing += "Telephone";
    if (valid != false) document.info_request.tel.focus();
    valid = false;
  }
  if (document.info_request.email.value == "") {
    if (valid == false) missing += ", "
    missing += "Email";
    if (valid != false) document.info_request.email.focus();
    valid = false;
  }

  if (valid == false) {
    alert ("Please fill in the following field(s): "+missing+".");
  }
  else {
    var email = document.info_request.email.value;
    if (email != "")
    {
      if (email.indexOf(' ') == -1 
          && 0 < email.indexOf('@')
          && email.indexOf('@') + 1 < email.length) {
        return valid;
      }
      else {
        alert ('Invalid email address.')
        document.info_request.email.focus();
        valid = false;
      }
    }
  }
  return valid;
}