Lock element to bottom of containing div [duplicate]

You can use relative absolute positioning:

http://jsfiddle.net/gzJM6/

#Container {
    width: 500px;
    height: 600px;
    position: relative
}

#TheElement {
    width: 500px;
    height: 100px;
    background-color: #000000;
    position: absolute;
    bottom: 0;
    left: 0;
}