I have this div box right now:
div#main-edit{
padding:2px 6px 4px 6px;
color: #555555;
background-color: #FFF8F8;
border: #dddddd 2px solid;
width: 750px;
height: 500px;
margin-left: 10%;
margin-right: 10%;
}
What I wanted now was to have another div box inside this div box, with its position being relative to its parent. Like This: 
Make your second div
height: 100%, and give your outer div padding all around.http://jsfiddle.net/P2VGk/