Edit in JSFiddle

body {
    padding:20px 50px;
    background-color:gray;
}

.accordion {
    position:relative;
    background-color:white;
}

.accordion > input {
    display:block;
    margin:0 0;
    width:100%;
    height:30px;
    position:relative;
    cursor:pointer;
    opacity:0;
    filter:alpha(opacity=0);
}

.accordion > label {
    display:block;
    font:bold 12px/30px Arial,Sans-Serif;
    background-color:black;
    color:white;
    margin:-30px 0 0 0;
    padding:0 15px;
}

.accordion > div {
    padding:10px 15px;
    display:none;
}

.accordion > input:checked + label {
    background-color:darkblue;
}

.accordion > input:checked + label + div {
    display:block;
}