function validContactForm() {
    if(document.getElementById('name').value.length < 1) {
        alert('Name is required.');
        document.getElementById('name').focus();
        return false;
    }

    if(document.getElementById('tel').value.length < 1) {
        alert('Phone number is required.');
        document.getElementById('tel').focus();
        return false;
    }

    with(document.getElementById('email')) {
        if(value.length < 1) {
            alert('E-mail address is required.');
            document.getElementById('email').focus();
            return false;
        }

        apos = value.indexOf("@");
        dotpos = value.lastIndexOf(".");

        if(apos < 1 || dotpos-apos < 2) {
            alert('E-mail address you entered is incorrect.');
            focus();
            return false;
        }
    }

    if(document.getElementById('city').value.length < 1) {
        alert('City name is required.');
        document.getElementById('city').focus();
        return false;
    }

    return true;
}