#horizon {
position: absolute;
top: 50%;
left: 0px;
width: 100%;
height: 1px;
overflow: visible;
background-color: transparent;
text-align: center;
}

#content {
position: absolute;
top: -225px;
left: 50%;
margin-left: -375px;
background-color: white;
width: 750px;
height: 450px;
text-align: left;
}