If the ISMAP attribute is present on an <IMG> element, the <IMG> element must be contained in an <A> element with an HREF present. This construct represents a set of hyperlinks. The user can choose from the set by choosing a pixel of the image. The user agent computes the head URI by appending `?' and the x and y coordinates of the pixel to the URI given in the <A> element. For example, if a document contains:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <head><title>ImageMap Example</title> <BASE HREF="http://host/index"></head> <body> <p> Choose any of these icons:<br> <a href="/cgi-bin/imagemap"><img ismap src="icons.gif"></a>
and the user chooses the upper-leftmost pixel, the chosen hyperlink is the one with the URI `http://host/cgi-bin/imagemap?0,0'.