SOURCE

<div class="wrapper">
	<div class="inner">test</div>
</div>

.tcenter{
  text-align:center;
}
.lh100{
  line-height:100px;
}
.flexCenter{
  display:flex;
  align-items:center;
  justify-content: center;
}
.marginHCenter{
  margin:0px auto;
}
.positionHCenter{
  position:absolute;
  left:50%;
  margin-left:-50px;
}
.positionVCenter{
  position:absolute;
  top:50%;
  margin-top:-50px;
}
.positionHCenterTranslate{
  margin:0;
  position:absolute;
  left:50%;
  transform:translate(-50%, 0);
}
.positionVCenterTranslate{
  margin:0;
  position:absolute;
  top:50%;
  transform:translate(-50%, -50%);
}

.wrapper{
  width:100%;
  height:200px;
  border:1px solid red;
  position:relative;
}
.inner{
  width:100px;
  height:100px;
  color:white;
  background:green;
}