<!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>
<title></title>
<!-- <style type="text/css">
/*标签选择器*/
div
{
300px;
height: 200px;
background-color: Green;
border: 1px dashed red;
}
/*类选择器*/
.cls
{
background-color: Black;
}
/*id选择器*/
#dv
{
background-color: Yellow;
}
/*标签选择器<类选择器<id选择器==优先级别,*/
</style>-->
<script type="text/javascript">
</script>
<link href="01.css" rel="stylesheet" type="text/css" />
</head>
<!--元素和元素之间的距离用margin-->
<body style="margin: 0">
<!--div是块级元素,层，非块级元素<span></span>-->
<!-- style=" height:300px; background-color:Green; 300px; border:2px solid red;"-->
<div class="cls" id="dv">
</div>
</body>
</html>