Deep Web (sometimes referred to as the invisible Web and the hidden Web) - part of the web pages of the World Wide Web sites that are not indexed by search engines. In addition, there is even more mysterious phenomenon - Dark Web, which are to network segments that are not connected to the Internet.Invisible Internet exists in a number of reasons, among them - the reasons, both technical and organizational nature. Some resources can be indexed by search engines, from a technical point of view, but they simply have not yet
managed to locate the page content. Some types of content are not indexed by search engines because «spider» deliberately set to ignore these or other resources. Some pages have a format that is not yet supported by search engines.
Deep Web in volumes greater than normal at 400-500 times. Search robots index of about 16 per cent of the total web content. The deep web better (on average three times the normal quality). And yet the deep Web is growing fastest.
According to different authors seem to include Internet content around 20-30% of the Network. The most daring sources referred to as a figure of no more than 50%. Thus, one could argue that the Invisible Web - this is the bulk of resources available online.
