var image1_on = new Image;     
image1_on.src ="img/menu/a2_on.gif";

var image1_off = new Image;
image1_off.src ="img/menu/a2.gif";

var image2_on = new Image;     
image2_on.src ="img/menu/b3_on.gif";

var image2_off = new Image;
image2_off.src ="img/menu/b3.gif";

var image3_on = new Image;     
image3_on.src ="img/menu/b4_on.gif";

var image3_off = new Image;
image3_off.src ="img/menu/b4.gif";

var image4_on = new Image;     
image4_on.src ="img/menu/b5_on.gif";

var image4_off = new Image;
image4_off.src ="img/menu/b5.gif";

var image5_on = new Image;     
image5_on.src ="img/menu/a6_on.gif";

var image5_off = new Image;
image5_off.src ="img/menu/a6.gif";