Back-links are an important aspect of any marketing effort. You want people to find your website or web page, after all, this is why you created it in the first place. Therefore, you need to create several ways for people to find it. The search engines love this. When the search engines see the link on someone else's site or elsewhere, they send the spiders or web crawlers over to your site and index your site. This means that your site gets placed on a search engine automatically rather than you entering it yourself, which is actually the way the search engines prefer it. Remember, the number of quality back links to a website or web page is one of the most important factors that determine its rank on the search engine.