e is introduced as spacing above the top margin after margin collapsing occurs." />
        <style type="text/css">
            #div1
            {
                height: 2in;
                width: 2in;
            }
            #div2
            {
                background: red;
            }
            #div3
            {
                margin-top: 1in;
                margin-bottom: 1in;
            }
            #div4
            {
                background: green;
                clear: right;
  