Email spiders work by crawling the web search for special characters like the ‘@’ sign and try to collect as many email addresses as possible.
This simple and little plugin converts email address in your page header, title, content and comments into HTML conform ASCII values. The email address will still appear as it normally would, but if you look at the page source you will only see the ASCII representation of the address. If you want to try this for your self, view this page source in Internet Explorer (sorry not Firefox, its source viewer converts the ASCII back to plain old text for you) and scroll to this email address below.
ASCII Email —> firstname.lastname@example.org <—