*Good affiliate marketing has a lot to do with good web site design. Read and follow the guidelines for making your site usable and accessible and keep your web site, as well as access to it, up-to-date.
One way to keep people on your site is to create a custom error page. When people try to get to your site by clicking an old link and see the standard "page not found" message (called a 404 error), many will assume that the site is down or has been removed. As a result, they're likely to click away and visit a different site, causing you to lose potential affiliate income. When you instead present them with a page that looks like your site (providing them with your navigation and a specific message directing them to your main pages), however, you'll regain that traffic you would have otherwise lost.