HTML & XHTML: The Definitive Guide, 6th Edition

Inserting Images in Your Documents

One of the most compelling features of HTML and XHTML is their ability to include images with your document text, either as intrinsic components of the document (inline images), as separate documents specially selected for download via hyperlinks, or as background to your document or elements within the document. When judiciously added to the body content, images—static and animated icons, pictures, illustrations, drawings, and so on—can make your documents more attractive, inviting, and professional looking, as well as informative and easy to browse. You may also specially enable an image so that it becomes a visual map of hyperlinks. When used to excess, however, images make your document cluttered, confusing, and inaccessible, and they unnecessarily lengthen the time it takes for users to download and view your pages.

Understanding Image Formats

Neither HTML nor XHTML prescribes an official format for images. However, the popular browsers specifically accommodate certain image formats: GIF, PNG, and JPEG, in particular (see the following sections for explanations). Most other multimedia formats require special accessory applications that each browser owner must obtain, install, and successfully operate to view the special files. So it’s not too surprising that GIF, PNG, and JPEG are the de facto image standards on the Web.

Both image formats were already in widespread use before the Web came into being, so there’s lots of supporting software out ...