body { 
  margin: 0 auto;
}

.un-10 {
  height: 100px;
  border: 1px solid grey;
  float: left;
  width: 100px;
}

.un-20 {
  height: 200px;
  border: 1px solid grey;
  float: left;
  width: 200px!important;
}

.un-30 {
  height: 300px;
  border: 1px solid grey;
  float: left;
  width: 300px!important;
}

.un-40 {
  height: 400px;
  border: 1px solid grey;
  float: left;
  width: 400px!important;
}

.un-50 {
  height: 500px;
  border: 1px solid grey;
  float: left;
  width: 500px!important;
}