<body>
<div class="father">
</div>
</body>
.father{
background-color:red;
position:absolute;
left:0;
right:0;
top:0;
bottom:0;
}<body>
<div class="father">
</div>
</body<body>
<div class="father">
</div>
</body>
.father{
background-color:red;
position:absolute;
left:0;
right:0;
top:0;
bottom:0;
}<body>
<div class="father">
</div>
</body