Prevent Spammers from Leaving Junk Comments on Website

I need someone who can prevent spammers from leaving junk comments on my website. I am open to your suggestions for solving the problem. I need a simple quick solution **IMPORTANT EDIT: I also need all existing spam comments removed from the website. (I do not mind if I lose any existing legitimate comments. ** In your Bid please provide a brief description of how you intend to fix the problem and your cost for doing so. After the problem is fixed, I will also need a written step by step explanation of how you solved the problem so that I can repeat the process on a similar site. Here is a sample page with spam comments:? <[login to view URL]> Thanks