imglist = ["/image/menu01_over.gif", "/image/menu02_over.gif", "/image/menu03_over.gif", "/image/menu04_over.gif", "/image/headernavi01_over.gif", "/image/headernavi02_over.gif", "/image/headernavi03_over.gif"];
preImage = new Array();
for (i=0; i<imglist.length; i++) {
  preImage[i] = new Image();
  preImage[i].src = imglist[i];
}