How To Make An Element Move Diagonally (i.e. Hold "Up" and "Right" Arrow Keys) With Arrow Keys

I have everything setup so that whenever I hold one of the Arrow Keys, my DIV will move in the direction that I push. But when I hold one of the Arrow Keys, and then hold another one at the same time (i.e. Up and Right) the DIV only moves in the direction that was first pushed, instead of moving Diagonally.