The Web is based on the concept of hypertext. A hypertext document allows readers to access information in the document in almost any order, unlike a traditional linear text which is intended to be read from beginning to end. For example, suppose you are reading a research paper on computational fluid dynamics. A traditional paper might have an introduction, a definition of terms, some equations, some algorithms that implement the equations, and a discussion of the performance of the algorithms on one or more supercomputers. If you are an expert in this area, you might want to skip the definitions and equations and go right to the algorithms. As you are reading that section you might decide you shouldn't have skipped the equations after all, and want to go back and read them. Hypertext is intended to make these random movements through the document easier for the reader. The idea is to give the reader more of a role in deciding how to use the document and to make the document flexible enough to be used in several ways (e.g. as a textbook the first time it is read and later as a reference book).