webBrowser1.Document.GetElementById("Qautodriving").SetAttribute("checked", "true");
update_auto_driving()
<script type="text/javascript"> var frm = document.forms.join; function update_auto_driving() { if (get_radiobutton(frm.elements.Qautodriving) == 1) { get_myelement("auto_owner_div").display = "block"; get_myelement("auto_user_div").display = "block"; } else { get_myelement("auto_owner_div").display = "none"; get_myelement("auto_user_div").display = "none"; } } update_auto_driving(); </script>