Create CAPTCHA Images - Tutorial
Worried about bots? Then create CAPTCHA images to prevent bots from taking advantage of your site. You may be wondering what a CAPTCHA image is. Here's a brief synopsis from Wikipedia:
A captcha (an acronym for "completely automated public Turing test to tell computers and humans apart") is a type of challenge-response test used in computing to determine whether or not the user is human. Captchas are used to prevent bots from using various types of computing services. Applications include preventing bots from taking part in online polls, registering for free email accounts (which may then be used to send spam), and, more recently, preventing bot-generated spam by requiring that the (unrecognized) sender pass a captcha test before the email message is delivered.