function newImage(arg) {
if (document.images) {
rslt = new Image();
rslt.src = arg;
return rslt;
}
}

function changeImages() {
if (document.images && (preloadFlag == true)) {
for (var i=0; i<changeImages.arguments.length; i+=2) {
document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
}
}
}

var preloadFlag = false;
function preloadImages() {
if (document.images) {
mainnavi_home_over = newImage("img/mainnavi_home-over.gif");
mainnavi_current_e_over = newImage("img/mainnavi_current_e-over.gif");
mainnavi_past_e_over = newImage("img/mainnavi_past_e-over.gif");
mainnavi_search_e_over = newImage("img/mainnavi_search_e-over.gif");
preloadFlag = true;
}
}