In order to get it to work in FF, you simply need to add vertical-align: top
to the .whitebox
element. Since it is a table-cell
element, it will respect the vertical-align
property and align itself as you would expect.
.jumbotaboverlay .whitebox {
background-color: white;
border: 1px solid black;
display: table-cell;
width: 50%;
height: 100%;
vertical-align: top;
}
In regards to your other question, it is completely dependent on what browsers you are trying to support.