Advanced Honeypot Fields: Stop Spam Without Annoying The User

Most spam bots aren't too smart and will fill all the fields they find in a form in attempt to spam it. This led to inventing super-simple "honeypot" fields - input fields hidden by CSS. Users don't see them and don't fill them, while bots fill them. In your backend you just have to check if the field is empty. If it is not, voila, you have caught a spammer.