function contact_form_validate(form) {
    var error = '';
    if( form.txtName.value.length < 2 ) {
        error += 'Please enter Name.\n';
    }
    if( form.txtCompany.value.length < 2 ) {
        error += 'Please enter Company.\n';
    }
    if( form.txtTel.value.length < 8 ) {
        error += 'Please enter Phone Number.\n';
    }
    if( form.txtEmail.value.length < 6 ) {
        error += 'Please enter Email.\n';
    }
    if( form.txtPeople.value == '' ) {
        error += 'Please enter Number of People.\n';
    }
    
    if( form.getSelectedProps.value && typeof(document.properties_form) == "object" ) {
        var checkboxes = document.properties_form.elements['selectedProps[]'];
        var selected = '';
        for( var i = 0; i < checkboxes.length; i++ ) {
            if( checkboxes[i].checked ) {
                if( selected == '' ) {
                    selected = checkboxes[i].value;
                }
                else {
                    selected = selected + ',' + checkboxes[i].value;
                }
            }
        }
        form.selectedPropIds.value = selected;
    }
    
    if( error == '' ) {
        form.hidRequest.value="submit";
        form.submit();
    }
    else {
        alert(error);
    }
}