求大神帮忙看下为什么有的部分没有效果
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>用CSS来控制</title>
<style>
#lside{width: 200px;
height: 300px;
background-color: red;
float: left;
}
#rside{width: 200px;
height:300px；
background-color: green;
float: left;
}
#common{width: 200px;
height:300px；
background-color: blue;
}
</style>
</head>
<body>
<div id="lside">我是左边</div>
<div id="rside">我是右边</div>
<div id="common">我是普通</div>
</body>
</html>
