i m thinking of making a website..and i want to keep a track on the sent messages! what if some human and not a computer is sending messages that are nt at all subject related..any way to stop that! [apart from the public cooperation]
as in how does stackoverflow keeps track of spams.. how it makes sure that the message sent is totally to the point and subject related!
CAPTCHA. It's implementation depends on what software you're using. reCAPTCHA is often used as it's easy to setup and use.
Every time a user submits something through your website you should check for spam. You can be sure that as soon as your web site is on the web, spam robot will crawl trough it and submit every form they see.
Now, there are various ways to counter their attack. A very simple way is to add captcha to your form. But captcha aren't that effective and user tend to hate them. Another way is to let them submit, but then an administrator must approve their submission. Other site uses email to make sure user are authentic (forum registration for example). Other site blocks IPs that submit too many forms in x amount of time.
As you can see there is a lot of different techniques (and I haven't list them all). You need to choose the one that would work best for you.
One thing I have done is use a time interval for valid messages. That is, start a timer when the form loads, and have a set determined interval (based on the length of the form) between when a response would be considered valid, and when it wouldn't. If it falls outside of those bounds, then prompt with a CAPTCHA as others have suggested. It's just an extra layer in the honeypot.