The guts of a client-side image map are the <area> tags within the map segment. These <area> tags define each mouse-sensitive region and the action the browser should take if that region is selected by the user in an associated client-side image map.

The region defined by an <area> tag acts just like any other hyperlink: when the user moves the mouse pointer over the region of the image, the pointer icon will change and the browser displays the URL of the related hyperlink in the status box at the bottom of the browser window.[*] Regions of the client-side image map not defined in at least one <area> tag are not mouse-sensitive.

[*] That is, unless you activate a JavaScript event handler that writes the contents of the status box. See the onMouse event handlers in 7.5.4.6.