Измените свой CSS на это
#green
{
position: relative;
float : left;
width : 20px;
top:100%;
margin : 5px;
border: solid 1px #0fb551;
background: -webkit-gradient(linear, 0 0, 0 bottom, from(#0fb551), to(#064d23));
background: -moz-linear-gradient(#0fb551, #064d23);
background: linear-gradient(#0fb551, #064d23);
-pie-background: linear-gradient(#0fb551, #064d23);
behavior: url(pie.htc);
}
Add some jQuery to your project
$(function(){
$('#graph div').each(function(){
var ht=$(this).height();
$(this).css({'margin-top':-ht-4+'px'});
});
});