Learnt about something new today. Its called CAPTCHA ! hmmm... got linked into it from my yahoo mail account. Was sending out a mail when i was made to enter a word into a text box from an image. This was apparently for security against spam (as i was mailing to one mail group that i belonged to).

CAPTCHA stands for 'Completely Automated Public Turing Test for Telling Computers and Humans Apart'. So what they do is generate an image with a randomly generated word in it. Its difficult for most existing programs to guess the words accurately from its distorted form in the image. But humans easily comprehend the letters and are able to successfully enter the matching word to identify themselves to be 'HUMAN'!

Well this has proved its use mostly in online service providers' domain like online polls, account creation (with email providers for example) and spam protection.

Ref: http://www.captcha.net