McLuhan classed media as either hot or cool dependent on how high their level of interaction. Hot media have very low levels of interaction, whereas cool media demand a high level of interaction. While I do not agree with how he classed some media, such as classifying TV as a cool media, it does give a useful tool for classifying media.
The WEB potentially is a very cool media, as it can require high levels of interactivity and participation from the user, even to casting the user into the role of author.
This high level of interactivity will generate a significant shift way from our society's linearity, a product of the dominant print paradigm, for as McLuhan says feedback is the end of linearity.