How can I position my div at the bottom of its container?

Answer 1

If you do not know the height of child block:

#parent {
    background:green;
    width:200px;
    height:200px;
    display:table-cell;
    vertical-align:bottom;
}
.child {
    background:red;
    vertical-align:bottom;
}

    
child
    
 

http://jsbin.com/ULUXIFon/3/edit

If you know the height of the child block add the child block then add padding-top/margin-top:

#parent {
    background:green;
    width:200px;
    height:130px;
    padding-top:70px;
}
.child {
    background:red;
    vertical-align:
    bottom;
    height:130px;
}

    
child