Paypal Integration Problem - I am not getting any response from paypal website when transaction is done.

Set the paypal return URL in your Web config file in app settings like this.

<add key="ReturnUrl" value="http://localhost:3029/PayPal/PayPalSuccess.aspx" />

Refer this examples
http://www.codeproject.com/KB/aspnet/UsePayPalPaymentInASPNET.aspx
http://www.codeproject.com/KB/showcase/Embed-PayPal.aspx