There are a number of Web hosting companies that maintain
Web sites for other businesses and individuals, which can lead to
vast amounts of diverse content being located at the same IP
address. Hosting services are offered either for a fee, or in
some cases, for free, allowing any individual with Internet
access to create a Web site. Some hosting services are provided
through the process of "IP-based hosting," where each domain name
is assigned a unique IP number. For example, www.baseball.com
might map to the IP address "10.3.5.9" and www.XXX.com might map
to the IP address "10.0.42.5." Other hosting services are
provided through the process of "name-based hosting," where
multiple domain name addresses are mapped to a single IP address.
If the hosting company were using this method, both
www.baseball.com and www.XXX.com could map to a single IP
address, e.g., "10.3.5.9." As a result of the "name-based
hosting" process, up to tens of thousands of pages with
heterogeneous content may share a single IP address.
2. The Indexable Web, the "Deep Web"; Their Size
and Rates of Growth and Change

The universe of content on the Web that could be indexed, in
theory, by standard search engines is known as the "publicly
indexable Web." The publicly indexable Web is limited to those
pages that are accessible by following a link from another Web
page that is recognized by a search engine. This limitation
exists because online indexing techniques used by popular search
engines and directories such as Yahoo, Lycos and AltaVista, are
based on "spidering" technology, which finds sites to index by
following links from site to site in a continuous search for new