function checkvalues(form) {
if (document.form.naam.value == "") {
alert('please enter your name');
document.form.naam.focus();
return false;
}
if (document.form.telefoon.value == "") {
alert('please enter your telephone number');
document.form.telefoon.focus();
return false;
}
if (document.form.e_mail.value == "") {
alert('please enter your e-mail address');
document.form.e_mail.focus();
return false;
}
if ((document.form.e_mail.value.indexOf('@', 0 ) == -1)||
(document.form.e_mail.value.indexOf('.', 0 ) == -1)) {
alert('please enter a valid e-mail address in\n for example e-mail@address.com');
document.form.e_mail.focus();
return false;
}
form.submit();
}