Use this css to remove the space inbetween them at all on all browsers and then simply insert <br>'s in between the review divs and you'll be good to go. 
Code:
/*Review Divs*/
.summary{
border: 1px dashed black;
padding:2px;
width:220px;
margin-bottom:5px;
}
.review{
border-style:solid;
border-width:15px;
border-top:none;
padding:5px;
margin:0;
clear:both;
}
.numberone{
border-color:#066;
background:#dae9e9;
}
.even{
border-color:#ddd;
background:#eee;
}
.odd{
border-color:#999;
background:#ddd;
}
/*End Review Divs*/
/*Review Headers*/
h2{
margin:0;
width:100%;
}
h2 a:link, h2 a:visited{
text-decoration:none;
padding-left:4px;
float:left;
font-size:21px;
}
h2 a:hover{
text-decoration:underline;
background:none;
}
h2.numberone{
background: #066 url(images/bluebar.gif);
float:left;
}
h2.numberone a:link, h2.numberone a:visited{
color:#fff;
}
h2.even{
background: #ddd url(images/lightgraybar.gif);
float:left;
}
h2.even a:link, h2.even a:visited{
color:#000;
}
h2.odd{
background: #999 url(images/darkgraybar.gif);
float:left;
}
h2.odd a:link, h2.odd a:visited{
color:#000;
}
/*End Review Headers*/
/*Review Images*/
h2 img{
float:right;
margin-top:5px;
}
/*End Review Images*/
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