Empty div (with style: height) will not display

If you just want to add white space try this

<div style="height:400px; width:100%; clear:both;"></div>

FIDDLE

or you could just add padding to the body like body { padding-top: 400px; }

The css style you are looking for is min-height: 20px; By default a div without content will have a height of 0 due to the auto setting being the default which sizes itself to fit content.