CAPTCHA (or Captcha) is an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart, based on the word 'capture'. It was originally coined by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford. CAPTCHA is meant to stop machines and robots from accessing webpage functionalities; it is usually placed in a web page's signup form to ensure only human beings are signing up with the site. Often, it is based on the fact that computers find it difficult to recognize text when presented in image form. More research and advanced techniques of
OCR (Optical Character Recognition) are weakening the Captcha concept, which in turn forces further research on Captcha. HTML5's canvas
element opens up the possibility of decoding it through JavaScript programming.
PHP Ajax Cookbook
PHP Ajax Cookbook
Overview of this book
Table of Contents (16 chapters)
PHP Ajax Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Free Chapter
AJAX Libraries
Basic Utilities
Useful Tools Using jQuery
Advanced Utilities
Debugging and Troubleshooting
Optimization
Implementing Best Practices to Build Ajax Websites
Ajax Mashups
iPhone and Ajax
Index
Customer Reviews