大图的不同点击区域实现不同的超链接：

<img src="planets.gif" width="145" height="126" alt="Planets" usemap="#planetmap">

<map name="planetmap">

  <area shape="rect" coords="0,0,82,126" alt="Sun" href="sun.htm">

  <area shape="circle" coords="90,58,3" alt="Mercury" href="mercur.htm">

  <area shape="circle" coords="124,58,8" alt="Venus" href="venus.htm">

</map>