Bloggers who use Blogger.com’s service can now enable an option under Settings | Comments tab to add captcha to their blog. What is a captcha? According to WikiPedia:

A captcha (an acronym for “completely automated public Turing test to tell computers and humans apart”) is a type of challenge-response test used in computing to determine whether or not the user is human. The term was coined in 2000 by Luis von Ahn, Manuel Blum, and Nicholas J. Hopper of Carnegie Mellon University, and John Langford of IBM. A common type of captcha requires that the user type the letters of a distorted and/or obscured sequence of letters or digits that appears on the screen.

This can help you maintain a readable and clean comments on your blog and prevent automated comment spam. Text-based browser users won’t be able to add comment if you enable this feature. This is possibly the only major drawback, but well worth it to prevent comment spam.

Many people said that the additional effort visitors have to take to have their comment submitted discourage them to comment on a post. I disagree, if people have useful things to say, they are going to take this small step of which proves to be far more useful to keep the blog clean.

Links:

• Word Verification for Comments
• What is the word verification option?