<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>HTML 图片不存在则显示一个默认图片</title>
</head>
<img src="demo.png" οnerrοr="this.src='demo2.png'" />
<body>
</body>
</html>
效果图: