In the old days of world wide web, users preferred to visit web directory to find the site they are looking for. As a matter of fact, Yahoo!, one of the preferred destination for online users, started as a web directory. Nowadays, most online user base rely on search engines too along with link directories, to find what they're looking for.

When search engines started to become popular, they were heavily relied on KEYWORDs and METATAGs of the web page to determine the topic and relevance of the page. Webmasters discovered that by keyword stuffing into METATAGs and webpage content, they could improve their website position in search results for verious keywords. But search engines are smart!. Search engines caught up to the abuse and decided to ignore the METATAGs and rely instead on text content of web page. Webmasters then started to keyword stuffing in the webpage content, often writing them in the same color as the web page's background so for webpage visitors as well as search engines that content is invisible.

Again, search engines worked on that area and discovered the trick and decided that the best way to rank a web page's content and its topical relevance was to rely on inbound links from other web pages. The rationale behind this is that it is much more difficult to influence other people to link back to your website than it is to manipulate your own web page elements. In fact, inbound links are the foundation of Google's Pagerank