A "seo friendly" site is one where the site is designed in a way that the search engines 'like' it... sort of. I.e. they can index pages easily (without having to decode hard URLs like: /index.php?cat=3&article=481 (etc)), and the content and page design are kept separate (i.e. using a CSS-based design). It's hard to explain. I hope the following may help a bit: