Spam protection with CSS-Captchas

Most of all webmasters, which have contact forms, registration forms or online polls on their websites, know the problem: in a short time they are receiving spam. The reason is, that spammers are using so-called harvesters (also known as webcrawler, spider, robot, or bot). This is a special software, which is searching automatically through the WWW, analyzes websites and tries to fill out any discovered forms with spam.

With Captchas (Completely Automated Public Turing test to tell Computers and Humans Apart), a method, which is able to distinguish between a computer (bot) and a human, it is possible to prevent these spam in most cases.

Info: primarily i wrote this stylesheet just for fun early in 2000 with IE v5.01 and Windows95, as i started to deal with CSS. At that time i only tried to show mathematical symbols in browsers without the use of graphic images. But we can use this stylesheet just as well for captchas.

Alphanumeric and special charaters with CSS (Cascading Style Sheets):

Supported browsers: IE 5.01, 5.5, 6.0, 7.0, Mozilla/Firefox, NN7-9, Opera 7-9 (Windows XP pro)

See also: Complete example inclusive form and evaluation

Download: example1.zip