HTML, XHTML & CSS

Chapter 14: Working with Forms
In addition, many Web-oriented development environments, such as Visual
Studio, Web Expressions, ASP.NET, and so forth also include extensive form
design and processing components. These work like frameworks, too, but
generally require you to work within their overall environments to take
advantage of their often awesome capabilities.
CAPTCHA This!
CAPTCHA stands for completely automated public turing test to tell computers
and humans apart — in other words, it’s a way of interacting on the Web that
permits developers to assume (with great assurance) that the entity typing
input on the other end of a remote connection is a person and not a program.
CAPTCHA is an important technique used to verify that a person is providing
input (especially, updating sensitive or valuable information) to a Web form
or other user input mechanism. The reason for this technology is to stymie
spammers and phishers from creating bogus e-mail addresses and Web
accounts that they can then use to pursue their own malicious ends. You
may not need to use CAPTCHA on your Web pages, but you need to know
what it is and why it’s important.
Basically, CAPTCHA works by bending text in wavy lines and overlaying
extra strokes or black marks, so that while humans can read the copy they
must enter at the keyboard to prove their intelligence is at work, computer
programs generally can’t decipher and regurgitate the text involved. The
standard example from www.captcha.net appears as Figure 14-16 with the
words “overlooks inquiry” subjected to the aforementioned treatment.
Figure 14-16: The CAPTCHA
example from the home page
at www.captcha.net.
The Web site at www.captcha.net explains the technology in more detail,
and goes on to describe how you can use it to add another level of authentication
to your Web pages. It’s not necessary for simple forms, but any time
you let users set up accounts, manage account info, or access sensitive data
(personally identifiable information, or PII, such as Social Security numbers,
credit card numbers, account numbers, and so forth, are prime targets for
such protection), it’s a good idea to put CAPTCHA in the way of would-be
evildoers.
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