Our simple anti-spam "Light-CAPTCHA"
Using Graphical CAPTCHAS prevents accessibility and gets very user unfriendly (frustration),
"war's" against robots makes CAPTCHAS harder to read for Humans then Robots.
This solution is simple but it may help you to reduce the SPAM.
As Form Robots tend to fill all possible fields in Form's this time I came up with idea "I'm a robot" needs to be unchecked in order to submit the Form.
However this protection is extended even more, there is a CSS display:none hidden form filed called "nocomments",
this is not visible for "normal" users but probably visible for Form Robots.
I suppose they can't resist without filling the form field named nocomments, that must be empty.
label for="registration_nocomment">Leave This Field Empty
input id="registration_nocomment" value="" name="nocomment" />
At present time the SPAM has got down 100% :-)
I have developed even an advanced PHP function creating special "serial number" for Form's and I will write about this in PHP section of tutorials.