cmvkk·13 ปีที่แล้ว·discussHere's my favorite explanation of this formula:http://betterexplained.com/articles/intuitive-understanding-...
cmvkk·16 ปีที่แล้ว·discussUnless doing it this way is actually more effective at reducing spam than a normal captcha, then it seems like this is just an intrusive advertising measure rather than anything useful. The potential for abuse just seems too great.
http://betterexplained.com/articles/intuitive-understanding-...