#element1
{
    width: 600px;
    border: 3px solid black;
    position: absolute;
    background-color:skyblue;
}
#element2
{
    width: 400px;
    height: 400px;
    background-color: red;
    position: relative;
    left: 100px;
    right: 100px;
    top: 100px;
    bottom: 100px;
}
#element3
{
    width: 600px;
    height: 600px;
    border: 3px solid black;
    background-color: skyblue;
    float: left;
    position: absolute;
    margin-top: 300px;
}
#element4
{
    width: 100px;
    height: 100px;
    background-color: red;
    position: relative;
    left: 250px;
    right: 250px;
    top: 250px;
    bottom: 250px;
    float: left;
    margin-top: 300px;
}