var img=new Array();
img[0]=new Image();img[0].src="../../images/contactus/check_btn.gif";
img[1]=new Image();img[1].src="../../images/contactus/send_btn.gif";
img[2]=new Image();img[2].src="../../images/contactus/back_btn.gif";

img[10]=new Image();img[10].src="../../images/contactus/check_btn_on.gif";
img[11]=new Image();img[11].src="../../images/contactus/send_btn_on.gif";
img[12]=new Image();img[12].src="../../images/contactus/back_btn_on.gif";

function change_image(aaa,num) {
document.images[aaa].src=img[num].src;
}