Introduction: Outline of our context

In most of our articles, we will restrict ourselves to a specific part of the website, namely the graphical appearance, viewable by all visitors. Even if the ergonomics of a website can affect its appearance and style, we will deal with it as if it were completely independent for simplicity and relevance of discourse.

Currently the "Web 2.0" is the dominant model of the web. It is characterized by rich and varied content written mainly by users themselves (this is often called User Generated Content or UGC). The major players in the web are no longer large corporations that would use Internet only as a supplementary channel to their existing media channels, but the vendors of native Web platforms, coming mostly from the computer industry ( Google, Yahoo, Microsoft ...). The Internet user now has access a wide range of free and paying services to express his ideas, react to news or find information about his interests. Methods to diffuse content on the Web have become simpler and easier during the past 15 years. It is indeed no longer necessary to be technically-savvy to broadcast information on the Internet.