/* Size the divs */
div { width:  50px; height: 50px; }

/* Colors */
div.green   { background: lightgreen; }
div.blue    { background: lightblue;  }
span.yellow { background: yellow;     }

/* Positioning */
.abs { position: absolute;    }
.rel { position: relative;    }
.in  { display: inline-block; }
.pos { top:  0px; left: 0px;  }