Digg.com is a very successful article review site among Web 2.0 websites, combining bookmarks, blogs, RSS, and non-hierarchical comment moderation. Its uniqueness lies in the fact that it doesn't have professional site editors; all editing depends on users. Users can submit articles freely, and then readers determine whether the article is useful. The more users who bookmark an article, the hotter the article is. In other words, if users think the article is good, they can "digg" it. When the number of diggs reaches a certain level, the article will appear on the homepage or other pages.