This example uses the (Beta) Asirra Project to determine if the form-filler is human or machine. Asirra (Animal Species Image Recognition for Restricting Access) is a HIP (Human Interface Proof) that works by asking users to identify photographs of cats and dogs.
If the cats are selected incorrectly, the message is not sent. In this demonstration, if the selection is wrong, an alert is given.
For Asirra to function for the user JavaScript must be running in the browser, and Asirra also requires server side coding. More information is at http://research.microsoft.com/asirra/
This page shows what happens when JavaScript is enabled: JavaScript disabled version
Note: This form does not submit any data to anywhere. It is for demonstration purposes only.