img标签usemap属性
html的img标签：定义一个图像在网页中引入。它还有个usemap属性很有意思。
看看51ditu首页中有一个地图，中部有个中国地图。点击右键下载下来看下就是一个普通的图片。
但点击地图上的省份却可以出发不同的事件（或打开不同的链接），很有意思。原来是使用了usemap属性。
当然还要定义一个map标签。整份代码如下：
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>img usemap属性</title>
</head>
<body>
<img src="http://www.51ditu.com/maps/img/chinamap.gif?n%A3%BDm" usemap="#Map" border="1"/>
<map name="Map" class="maparea">
<area shape="rect" coords="73,87,103,104" href="javascript:alert('新疆')">
<area shape="rect" coords="144,125,173,142" href="javascript:alert('青海')">
<area shape="rect" coords="84,158,115,175" href="javascript:alert('西藏')">
<area shape="rect" coords="220,90,257,105" href="javascript:alert('内蒙古')">
<area shape="rect" coords="348,45,389,61" href="javascript:alert('黑龙江')">
<area shape="rect" coords="346,68,371,83" href="javascript:alert('吉林')">
<area shape="rect" coords="323,84,351,100" href="javascript:alert('辽宁')">
<area shape="rect" coords="298,100,326,114" href="javascript:alert('天津')">
<area shape="rect" coords="288,120,314,136" href="javascript:alert('山东')">
<area shape="rect" coords="268,107,295,121" href="javascript:alert('河北')">
<area shape="rect" coords="207,116,235,130" href="javascript:alert('宁夏')">
<area shape="rect" coords="186,162,214,179" href="javascript:alert('四川')">
<area shape="rect" coords="256,142,281,157" href="javascript:alert('河南')">
<area shape="rect" coords="305,144,332,159" href="javascript:alert('江苏')">
<area shape="rect" coords="320,162,342,177" href="javascript:alert('上海')">
<area shape="rect" coords="216,168,243,185" href="javascript:alert('重庆')">
<area shape="rect" coords="250,162,277,177" href="javascript:alert('湖北')">
<area shape="rect" coords="283,161,308,177" href="javascript:alert('安徽')">
<area shape="rect" coords="213,196,239,209" href="javascript:alert('贵州')">
<area shape="rect" coords="243,183,269,198" href="javascript:alert('湖南')">
<area shape="rect" coords="273,185,299,200" href="javascript:alert('江西')">
<area shape="rect" coords="308,177,334,193" href="javascript:alert('浙江')">
<area shape="rect" coords="179,210,204,225" href="javascript:alert('云南')">
<area shape="rect" coords="227,214,252,228" href="javascript:alert('广西')">
<area shape="rect" coords="231,248,257,263" href="javascript:alert('海南')">
<area shape="rect" coords="292,200,319,214" href="javascript:alert('福建')">
<area shape="rect" coords="259,219,287,231" href="javascript:alert('广东')">
<area shape="rect" coords="244,231,270,246" href="javascript:alert('澳门')">
<area shape="rect" coords="276,232,304,248" href="javascript:alert('香港')">
<area shape="rect" coords="311,228,338,243" href="javascript:alert('台湾')">
<area shape="rect" coords="272,90,302,107" href="javascript:alert('北京')">
<area shape="rect" coords="196,130,222,145" href="javascript:alert('甘肃')">
<area shape="rect" coords="246,116,272,130" href="javascript:alert('山西')">
<area shape="rect" coords="224,136,252,151" href="javascript:alert('陕西')">
</map>
</body>
</html>
map标签里的area标签的几个属性意义见：http://www.w3school.com.cn/tags/tag_area.asp
这里还是记下area的shape属性，可选项有矩形，圆形和多边形。尤其要注意的是coords属性，得结合shape使用，图像左上角的坐标是 "0,0"。