#slideshow
{
    margin: 0 auto;
    position: absolute;
    z-index: -1;
    margin-top: 15px;
    width: 1170px;
    height: 400px;
    background-color: lightgray;
    opacity: 0.2;
}
#joinus
{
    height: 80px;
    width:  200px;
    background-color: black;
    margin-top: 120px;
}