CAPTCHA

You may have signed up for a service on the Internet such as a web mail service and at the end of the form you fill in you will see some strange characters for you to type in - this technique is known as CAPTCHA

Basically what this does is it makes sure that the person typing in the details is a "real person" and not a computer filling in the form. This cuts down on junk emails and false account setups on web sites.

You may also see these symbols on web sites where you can make comments.