Codecademy Sample Solution: Codeyear Recap of the difference...

/* sample solution to style.css */

/* a border for each div so you can see what's going on */

#parent{
    border:1px solid black;
    background: red;
    height: 100px;
    width: 100px;
    margin-left:100px;
    position: fixed;
    top: 76%;
    left: 68%;
}

#child{
    position:absolute;
    background: yellow;
    top: 15px;
    left: 15px;
    bottom: 15px;
    right: 15px;
}