Although many people first go to the Web for information, it is not always the best place for what you need.

Most information on the Web does not go through a review process.
Anyone can publish on the Web without passing the content through an editor. Pages might be written by an expert on the topic, a journalist, a disgruntled consumer or even a child.  And some sites that do have a review process can have weak standards.  For example, the editors of Wikipedia do not always have expert knowledge for the articles that they review, and they end up relying upon any volunteer to edit or correct an entry.

Some information on the Web is not free.
Many Web pages are free to view, but some commercial sites will charge a fee to access their information.

Information on the Web is not organized.
Some directory services, like Yahoo, provide links to sites in subject lists. But there are too many Web pages for any single directory service to organize and index.

Most information on the Web is not comprehensive.
Rarely will you be able to use a search engine on the Web to collect information about your topic from earlier decades and different types of sources.

Most information on the Web is not permanent.
Some well-maintained sites are updated with very current information, but other sites may become quickly dated or disappear altogether without much if any notice.