我有以下HTML：
<!DOCTYPE html>
<html>
<head>
<Meta charset="UTF-8">
<title>:before pseudo-class and images</title>
<style type="text/css" media="screen">
img {
display: block;
width: 640pt;
}
img:before {
content: "Test";
}
</style>
</head>
<body>
<img src="http://andreygromov.name/picture/flower/flower4.jpg" alt="Ваза с цветами" />
</body>
</html>
：之前不会出现图像,但它适用于任何div.
为什么？
更新：
我在W3C中找到了这个解释：
Note. This specification does not fully define the interaction of :before and :after with replaced elements (such as IMG in HTML). This will be defined in more detail in a future specification.
更新2：
我忘了提 – 我需要用CSS可视化图像的“alt”属性.
img:before {
display: block;
content: attr(alt);
background-color: #333;
/* etc. */
}
