<!DOCTYPE html>
<html>
<head>
<title>书写css伪类时冒号后多个空格导致该规则失效</title>
<meta http-equiv="Content-Type" content="text/html;charset=gbk"/>
<style type="text/css">
a:link{color : gray;}
a:visited{color : red;}
/* 冒号后多了个空格 */
a: hover{color : yellow;}
</style>
</head>
<body>
<a href="http://www.sina.com">sina</a>
</body>
</html>
