Edit in JSFiddle

.slide {
    height:200px;
    width:300px;
    padding:1em;
    margin:1em auto;
    display:table;
}

.slide div {
    border:2px solid #fff;
    text-align:center;
    vertical-align:middle;
    display:table-cell;
    color:#fff;
    font-family:monospace;
    font-size:3em;
}
#slideshow1 {   
    background:#faa;
}
#slideshow2 {   
    background:#afa;
}
#slideshow3 {   
    background:#aaf;
}
#slideshow4 {   
    background:#000;
}