One of the mainest features in understanding Web 2.0 is transition to a semantic marking which accurately describes the information to which she concerns. The most popular languages of marking HTML and XHTML basically are used for display of the information. For this purpose tags to which it is possible to apply styles CSS are intended. However for the description of the various information of the given tags does not suffice: we have only the elementary paragraphs, headings, lists and, roughly speaking, all. And in Web 2.0 such descriptions not only are possible(probable), but also crucial!

As an example it is possible to result format RSS/XML for association of the information in the convenient form. It is a simple way to inform up to readers of a message about new materials on a site. It is necessary to subscribe only on RSS in the program for job with the similar data.