盒子模型+定位：div的使用，postion：fixed;定位的使用；
盒子模型的嵌套:div中div;
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style type="text/css">
*{
margin:0px;
padding:0px;
}
#div1{
width:200px;
height:200px;
border:2px solid green;
}
#div2{
width:200px;
height:200px;
border:2px solid red;
}
#div3{
width:200px;
height:200px;
border:2px solid yellow;
position:relative;
margin-top:40px;
}
#div4{
width:50px;
height:50px;
border:2px solid blue;
background-color:black;
}
#div5{
width:200px;
height:200px;
border:2px solid orange;
position:fixed;
right:50px;
top:50px;
}
</style>
</head>
<body>
<div id="div1">
<div id="div4">
div4
</div>
</div>
<div id="div2">
div2
</div>
<div id="div3">
div3
</div>
<div id="div5">
div5
</div>
</body>
</html>
來和小妲己一起學習鴨哒·······························
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