document.onimage1 = new Image();
document.onimage1.src="../image/common/home_a_02.gif";

document.onimage2 = new Image();
document.onimage2.src="../image/common/back_a_02.gif";

document.onimage3 = new Image();
document.onimage3.src="../image/common/home_b_02.gif";

document.onimage4 = new Image();
document.onimage4.src="../image/common/back_b_02.gif";