Position the middle div using absolute positioning without specifying height. It does not get much simpler than this:
#header {
position: fixed;
top: 0;
left: 0;
right: 0;
height: 100px;
background-color: #abcdef;
}
#footer {
position: fixed;
bottom: 0;
left: 0;
right: 0;
height: 100px;
background-color: #abcdef;
}
#content {
position: fixed;
top: 100px;
bottom: 100px;
left: 0;
right: 0;
background-color: #F63;
overflow: auto;
}
<div id="header"></div>
<div id="content"></div>
<div id="footer"></div>
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