Hi Eran,

here is the solution for this:

I used google Recaptcha

I will put the steps below, just to help other to integrate it, but it would be better to integrate it with your solution :).

in the dll source code (the webservice) i have added a method:

[WebMethod]
        [System.Web.Script.Services.ScriptMethod(ResponseFormat = System.Web.Script.Services.ResponseFormat.Json)]
        public bool ValidateCaptcha(string challengeValue, string responseValue)
        {
            Recaptcha.RecaptchaValidator captchaValidtor = new Recaptcha.RecaptchaValidator
            {
                PrivateKey = Convert.ToString(ConfigurationManager.AppSettings["ReCaptchaPrivateKey"]), // Get Private key of the CAPTCHA from Web.config file.
                RemoteIP = HttpContext.Current.Request.UserHostAddress,
                Challenge = challengeValue,
                Response = responseValue
            };

            Recaptcha.RecaptchaResponse recaptchaResponse = captchaValidtor.Validate(); // Send data about captcha validation to reCAPTCHA site.
            return recaptchaResponse.IsValid; // Get boolean value about Captcha success / failure.
        }

on the Page template 



  <script type="text/javascript" src="http://www.google.com/recaptcha/api/js/recaptcha_ajax.js">script>    <script type="text/javascript">   $(document).ready(function(){     
 Recaptcha.create("Public Key!!",
         "DivID", 
        { 
          theme: "red", 
          callback: Recaptcha.focus_response_field
         }
       );
   });
   script> 

in the body a Div for My Captcha
 <div id="DivID">
  <div> 

now edit the RVContactForm.js


replace the code for sending with this one (ajaxSubmit) with this below:

var captchaInfo =
         {
             challengeValue: Recaptcha.get_challenge(),
             responseValue: Recaptcha.get_response()
         };

 $.ajax
    ({
         type: 'POST',
         url: '/umbraco/webservices/RVContactFormMailer.asmx/ValidateCaptcha',
         data: JSON.stringify(captchaInfo),
         contentType: 'application/json; charset=utf-8',
         dataType: 'json',
         success: CAPTCHASuccess,
         error: CAPTCHAFail
             }); 

add 2 new functions:


function CAPTCHAFail(msg) {
     var str = 'say something';
 }
 function CAPTCHASuccess(msg) {
            if(msg.d==true)
 { var myMailerRequest= 'prepare some thing inside the message !!' // JSONify the js object - desirialize js object to MailerRequest object. the first param must be equal to the name of the input parameter in the web service method "SendContactForm"
                var data = JSON.stringify({ req: myMailerRequest });
                $.ajax({
                    type: "POST",
                    url: "/umbraco/webservices/RVContactFormMailer.asmx/SendContactForm",
                    data: data,
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: AjaxSucceeded,
                    error: AjaxFailed
                });
            }
     else {
         alert('Please enter a Correct Captcha');
                return;
            }
 } 
function AjaxSucceeded(result) {
     //some jquery transformation and animation for appending result !!
 }
 function AjaxFailed(result) {
    // tell the user about the failure !!
 }

hope it help some Umbracian around :)

Cheers,

Firas.