为什么两个convas没有叠在一起？求大神！！！
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>tinyHeart</title>
<style type="text/css">
body{
padding-top:10px;
}
.all_bg{
width:800px;
height:600px;
margin:0px auto;
}
#allconvas{
position:relative;
width:800px;
height:600px;
margin:0px;
}
#convas1{
position:absolute;
bottom:0;
left:0;
z-index:1;
}
#convas2{
position:absolute;
bottom:0;
left:0;
z-index:0;
}
</style>
</head>
<body>
<div class="all_bg">
<div id="allcanvas">
<canvas id="canvas1" width="800" height="600"></canvas>
<canvas id="canvas2" width="800" height="600"></canvas>
</div>
</div>
<script type="text/javascript" src="js/main.js"></script>
<script type="text/javascript" src="js/commonFunctions.js"></script>
<script type="text/javascript" src="js/background.js"></script>
<script type="text/javascript" src="js/ane.js"></script>
<script type="text/javascript" src="js/fruit.js"></script>
<script type="text/javascript" src="js/mom.js"></script>
<script type="text/javascript" src="js/collisior.js"></script>
<script type="text/javascript" src="js/baby.js"></script>
</body>
</html>
