A CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't:
It started as a way to prevent spam, and it does help separate man from machine.
Copied from the CAPTCHA website
CAPTCHAs have several applications for practical security, including (but not limited to):
Protecting Website Registration. Several companies (Yahoo!, Microsoft, etc.) offer free email services. Up until a few years ago, most of these services suffered from a specific type of attack: "bots" that would sign up for thousands of email accounts every minute. The solution to this problem was to use CAPTCHAs to ensure that only humans obtain free accounts. In general, free services should be protected with a CAPTCHA in order to prevent abuse by automated scripts.
Protecting Email Addresses From Scrapers. Spammers crawl the Web in search of email addresses posted in clear text. CAPTCHAs provide an effective mechanism to hide your email address from Web scrapers. The idea is to require users to solve a CAPTCHA before showing your email address. A free and secure implementation that uses CAPTCHAs to obfuscate an email address can be found at reCAPTCHA MailHide.
Preventing Dictionary Attacks. CAPTCHAs can also be used to prevent dictionary attacks in password systems. The idea is simple: prevent a computer from being able to iterate through the entire space of passwords by requiring it to solve a CAPTCHA after a certain number of unsuccessful logins. This is better than the classic approach of locking an account after a sequence of unsuccessful logins, since doing so allows an attacker to lock accounts at will.
Search Engine Bots. It is sometimes desirable to keep webpages unindexed to prevent others from finding them easily. There is an html tag to prevent search engine bots from reading web pages. The tag, however, doesn't guarantee that bots won't read a web page; it only serves to say "no bots, please." Search engine bots, since they usually belong to large companies, respect web pages that don't want to allow them in. However, in order to truly guarantee that bots won't enter a web site, CAPTCHAs are needed.
Ok, yeah I get it, CAPTCHA can be very useful. But for those of us who practically live online, having to fill out hundreds of these on a daily basis is a HUGE annoyance. Especially when they look like this.
Seriously? Can you read what that says? Does it say anything at all? How is anyone expected to pass this little "test?"
How about this one?
This CAPTCHA crap is getting out of hand. But this rant isn't just me screaming about how much I hate CAPTCHA, or the fact that I can't translate about half of the ones I come across. No, dear reader, I do have an ulterior motive for posting this.
Blogger by default enables CAPTCHA on every comment. It's an annoyance and will make readers, who would normally leave a comment on your blog, turn away in frustration. Or worse yet, they think they have left you a comment and move on, only to realize later that if they had waited a second longer a CAPTCHA screen would have appeared so they could verify they are real before posting their comment (or contest entry).
You don't need to have this enabled and it's really easy to remove.
I can already hear the moaning. "But what about spammers?"
I've had CAPTCHA disabled on my blog for a while now. Do I get a ton of spammers? Not really. And thanks to Blogger's semi-new "Anti-Spam feature", they have all but disappeared from my view.
If you're really that worried about it, turn on comment moderation. That way you have 100% control over what shows up under your post.
For my peace of mind, I use semi-moderation. Any comment on a post older than 10 days is moderated. Oddly enough, those were the post that would get spammed. Guess spammers think we wouldn't pay attention to what's been posted in the past. But again, thanks to Blogger's Anti-Spam feature, those are now caught even before I can moderate them. Muahahahaha. <--- my evil laugh.
So, how do you disable the CAPTCHA?
Simple. Go to "Settings" on your Blogger Dashboard and click on the link for "Comments."
Scroll down the page until you see, "Show word verification for comments?"
Now click No!
Then save your settings. Simple as that.
Now your blog will be that much more user friendly.