[Adam H]

its either :

.popupbody {
    background: none repeat scroll 0 0 #E1E1E1;
    border: 1px solid #E1E1E1;
    color: #3E3E3E;
    display: none;
    font: 11px Tahoma,Calibri,Verdana,Geneva,sans-serif;
    left: 0;
    min-width: 200px;
    padding: 4px;
    position: absolute;
    top: 1.5em;
    z-index: 1000;
}

or

.toplinks ul.isuser li.popupmenu ul li {
    margin: 0;
    position: relative;
    text-align: left;
    top: 0;
}

that you will need to edit depending on how you theme is done. It looks a bit messed up to me from that image so you might need to play with margin and padding in those two classes to get it looking nice.