Web directories are the perfect source of back links for the web masters. But it is also essential that the links from the directories maintain quality. The most popular web directories are the DMOZ or the open directory project and the Yahoo directory. Human-edited directories are more valued than the others. Web sites have to be submitted in the directories in the specific subcategory belonging to a main category. Some directories like niche directories are totally created for a particular niche. Paid inclusion in a directory requires money to list the site while free inclusion is totally free. Some directories offer featured listings; some require reciprocal links and some others will place the affiliate link of the web site. In general, directories drive more traffic to the web sites except for some link farms.