title: Invalid remote certificate while accessing PayPal Sandbox transaction service
body: <p>I am testing my application with PayPal sandbox.</p>
  
  <p>The URI I use for the transaction is <em><a href="https://sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick" rel="nofollow">https://sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick</a>.</em></p>
  
  <p>In my return page I read the data from PayPal then I form a new string to send back with <strong>cmd = _notify-validate</strong>.
  When I make a call to <em><a href="https://sandbox.paypal.com/cgi-bin/webscr" rel="nofollow">https://sandbox.paypal.com/cgi-bin/webscr</a></em> I am getting error saying "The remote certificate is invalid according to the validation procedure."</p>
  
  <p>I tried making a call to <em><a href="https://www.paypal.com/cgi-bin/webscr" rel="nofollow">https://www.paypal.com/cgi-bin/webscr</a></em> instead and it always return t "INVALID".</p>