Untitled

<style>
div{
  width:200px;
  height:200px;
}
#t1{
  background-color:gray;
}
#t2{
  position:relative;
  top:50%;
  left:50%;
  background-color:orange;
}
</style>
<body>
　<div id="t1"></div>
　<div id="t2"></div>
</body>