We have used RadCaptcha in our site. but it is always wrong the first time, or it doesn't work well.
The code
http://.../Telerik.Web.UI.WebResource.axd?type=rca&guid=9b09e8e7-e7e7-413c-95bb-a384298dd817
The code
<telerik:RadCaptcha ID=
"captcha"
runat=
"server"
ValidationGroup=
"addcomment"
ValidatedTextBoxID=
"txtCode"
>
<CaptchaImage RenderImageOnly=
"true"
PersistCodeDuringAjax=
"true"
/>
</telerik:RadCaptcha>
<asp:TextBox ID=
"txtCode"
runat=
"server"
/>
http://.../Telerik.Web.UI.WebResource.axd?type=rca&guid=9b09e8e7-e7e7-413c-95bb-a384298dd817