HI Mohammad Al Hoss
I understand what do you mean, but let me tell you something.
AS you wish request all the BODY (bitsEncode), its really hard to prevent when a thirdparty captcha control is refreshed. and as a matter of fact, the captcha is only a parameter of many parameters (normally) for get access to some site.
I think this link could help you to do your own local control captcha and avoid to request that web.
A CAPTCHA Server Control for ASP.NET[
^]
Best regards