Prevention From Hackers

This has been always struck in my mind to know the right ways to protect a site from hackers. How can anyone make sure that the site is protected from hackers. Is there any software for the same or some coding, programmes to protect the site from hackers. Because Hackers are those people which can cause a great loss to you. I have seen many websites that stores money like the first one - our Techulator. So how Mr Tony John protects his websites from hackers. I can assure myself to protect my computer from harmful virsus by installing an antivirus but what can we do to ensure ourself when it comes to websites.

This is the best one I found to discuss in the Forum section because mostly everyone here own a website. Hope to see a reply from the webmaster soon and also would like to request the members to list their own websites if they own any.