HTML & XHTML: The Complete Reference (Osborne Complete Reference Series)

Linking documents on the Web requires a consistent naming scheme. URLs provide the basic information necessary to locate an object on the Internet by including the host name , directory, filename, and access protocol. URLs are written in a regular format so that an address can be written for any object. A common shorthand notation, a relative URL, is particularly useful when creating links within a Web site. If a document's URL can be determined, whether it's relative or fully spelled out, it can be specified in an < a> tag to create an anchor from one document to another. Links within HTML/XHTML documents can be made with text or with images. A special type of clickable image, called an image map , allows areas of an image to be defined as "hot."

Simply linking documents together is the most basic form of hypertext. By using the link element, as well as the rel and rev attributes of the a element, you can create relationships between documents. So far, the link element primarily is used with style sheets.

Even if Web authors master all aspects of linking, a bigger picture remains to worry about. Chapter 17 covers various topics related to linking, including link management, < meta> information, and filtering, but theoretical limitations still exist. The Web is a chaotic environment, and navigating among documents and linking documents presents serious challenges to Web designers. In the future, some of these problems might be solved by URNs, URCs, and improved URLs, which, taken together, make up the uniform resource identifier (URI). However, until URNs or similar technologies are more readily available, HTML authors should be cautious about linking, and do what they can do to improve URLs and link forms.