Short for Completely Automated Public Turing test to tell Computers and Humans Apart, CAPTCHA is a protection that identifies humans from computers. A commonly used CAPTCHA is an image that is distorted that contains text that is easy for humans to read, but difficult or impossible for computers to read. In the picture to the right, is an example of a CAPTCHA.
In the above example, the visitor can identify and type in that the image shows "KDEY"; without this information being entered into the web page, a user would be unable to continue. Unfortunately, blind or hard of seeing visitors run into difficulties with CAPTCHA's because of the inability to read the letters shown in the image. To help these visitors gain access to a page protected by a CAPTCHA, an audible CAPTCHA will read the letters aloud to the visitor.