Everyone has encountered a captcha system. Even if you dont know what it is… It’s that bit of really annoying obscured text used in registration systems for sites like MSN Hotmail, Yahoo etc… that tries to establish users as real people as opposed to bots creating accounts for spamming etc…

The trouble is OCR is getting better and better, and it’s becoming harder to make captcha graphics that they can’t crack.. This also means it’s becoming harder for people to read the increasingly complicated images.

Based on work by Stu Nicholls and Eric Smith, I have implemented a PHP script that generates “CSS Text”. This is text that could not be read by reading the source code of the web page, but yet appears perfectly legible to any person reading the page. This could easily be used in a Captcha system or, for example, to obscfucate eMail addresses to prevent spam bots harvesting them.

See the demonstration at http://www.iross.net/csscaptcha/