.square, .circle {
  width: 100px;
  height: 100px;
    display: inline-block;
}
.circle {
  border-radius: 50%;
}
#blockRed {
  background-color: red;
  position: relative;
}
#blockYellow {
  background-color: yellow;
  position: relative;
}
#container {
  background-color: blue;
  margin: 0 auto;
  width: 400px;
}
 <div class='square' id='blockRed' style='top: 200px; left: 200px;'></div>