b1 = new Image();
b1.src = "images/b1_on.gif";
b2 = new Image();
b2.src = "images/b2_on.gif";
b3 = new Image();
b3.src = "images/b3_on.gif";
b4 = new Image();
b4.src = "images/b4_on.gif";
b5 = new Image();
b5.src = "images/b5_on.gif";
b6 = new Image();
b6.src = "images/b6_on.gif";