​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>img longdesc 属性</h1>
​
<!-- 描述与图片位于同一页面 -->
<img src="/i/logo/w3.png" alt="w3school.com.cn" width="90" height="90" longdesc="#w3logoExplained">
​
<!-- 描述位于外部页面 -->
<img src="/i/logo/w3.png" alt="w3school.com.cn" width="90" height="90" longdesc="w3logo.txt">
​
<!-- 该描述是外部页面中的若干描述之一 -->
<img src="/i/logo/w3.png" alt="w3school.com.cn" width="90" height="90" longdesc="http://example.com/desc#item3">
​
<!-- 描述包含在 data:URI 中 -->
<img src="/i/logo/w3.png" alt="w3school.com.cn" width="90" height="90" longdesc="data:text/html;charset=utf-8;,%3C!DOCTYPE%20html%3E%3Chtml%3E%3Chead%3E%3Ctitle%3EDescription%20of%20the%20Logo%3C/title%3E%3C/head%3E%3Cbody%3E%3Cp%3ESome%20description%20goes%20here%3C/body%3E%3C/html%3E">
​
<div id="w3logoExplained">
  <h2>图像 w3.png</h2>
  <p>这里是图片的描述...</p>
</div>
​
</body>
</html>
​