One of the great innovations the World Wide Web and HTTP brought to the Internet
was the ability to serve up multimedia to clients. The precursors to full-motion video
and CD quality sound were graphical images, in the Web-friendly Graphics
Interchange Format (GIF) and Joint Photographic Experts Group (JPEG) formats.
You can include images in HTML documents by using the image tag (<img>).The
image tag includes a link to the image file as well as pertinent information used to
display the image (for example, the image size). A typical image tag resembles the
following:

The preceding example would result in the image tmoore.jpg being displayed at
the location in the document where the tag appears. In this case, the image is in the
images directory of the current server and will be displayed without a border,
100 pixels wide by 200 pixels high. The alt attribute is used to provide a textual
equivalent for browsers that cannot display graphics (or whose users have
configured them not to).
Images can also be used as navigation aids—allowing the user to click certain parts
of an image to perform an action, display another document, and so on. For example,
a map of the United States could be used to help a user select their state—clicking a
state would bring up the applicable page for that state. Navigational images are
commonly referred to as image maps and require a separate map of coordinates and
geometric shapes to define the clickable areas.