#wrapper{
  position: relative;
  width: 100%;
  max-width: 310px;
  margin: 0 auto;
  background: pink;
  height: 240px;
}

#bluebox{
  position: absolute;
  right: 0px;
  top: 0px;
  background-color: blue;
  width: 111px;
  height: 60px;
}

#redbox{
  position: absolute;
  left: 0px;
  top: 0px;
  background-color:red;
  width: 61px;
  height: 60px;
}

#greenbox{
  position: absolute;
  bottom: 0px;
  background-color: green;
  width: 111px;
  height: 60px;
}

#yellowbox{
  position: absolute;
  bottom: 0px;
  right: 0px;
  background-color: yellow;
  width: 60px;
  height: 60px;
}