#loginbox{
position: fixed;
left: 0;
width: 180px;
margin:auto;
z-index: 100;
text-align: center;
}
#loginbox{
background:white url(/images/bkg-categorie.gif) no-repeat bottom left;
}
#loginbox input{
width: 80px;
margin-bottom: 5px;
}
#loginbox h3{
color:white;
background:#EC6F01 url(/images/bkg-categorie.gif);
padding:3px;
text-align:center;
}
#overlay{
position: fixed;
top: 0;
left: 0;
z-index: 90;
width: 100%;
height: 500px;
background-color: #000;
text-align: center;
}
.centeredMargin {
width: 180px;
left: 0;
margin-left: auto;
right: 0;
margin-right: auto;
background: red;
}

.verticalMargin {
height: 100px;
top: 0;
margin-top: auto;
bottom: 0;
margin-bottom: auto;
background: yellow;
}