function validateForm(f) {
var first_field = null;
var result = true;
try {
        var all = f.elements;
        $A(all).each(function(ifield){
                if (Element.hasClassName(ifield, "required_field")) {
if('' == ifield.value) { // need more strict empty value verification
 first_field = ifield;
result = false;
Element.addClassName(ifield, 'required_field_highlighted');
 } else { // reset to default style of border?
Element.removeClassName(ifield, 'required_field_highlighted');
}
}
        });
if (first_field) first_field.focus();
} catch (e) {}
return result;
}