 margin of an in-flow block-level element is always adjoining to the top margin of its next in-flow block-level sibling." />
        <style type="text/css">* { margin: 0; padding: 0 }
            div
            {
                font: 20px/1em Ahem;
                width: 5em;
            }
            div div
            {
                background: green;
                height: 1em;
            }
            #div1
            {
                background: url('support/margin-collapse-2em-