The World Wide Web is a large and rapidly growing space of documents composed of text, image, and sound.
Most search services provide exhaustive string or word searching.
Some of these index almost any Web site they find, others restrict their document space in some way. There are also services that provide a selective list of sites which they present within a hierarchical set of categories. Both types of services vary in the number and kinds of documents they index, in the search tools provided to the user, and in the way in which the results are presented. You need to be flexible about the ways in which you expect the data to appear and to be ready to be open-minded, yet critical with respect to content. Critical assessment and evaluation of information is an important skill to develop.