preroad() 
function preroad(){ 
f_name = new Array 
file = new Array 

//先行読みこみしたい画像分だけ要素数を追加する 
f_name[1] = "../img/menu/menu1_on.gif" 
f_name[2] = "../img/menu/menu2_on.gif" 
f_name[3] = "../img/menu/menu3_on.gif" 
f_name[4] = "../img/menu/menu4_on.gif" 
f_name[5] = "../img/menu/menu5_on.gif" 
f_name[6] = "../img/menu/menu6_on.gif" 
f_name[7] = "../8img/menu/menu7_on.gif" 
f_name[8] = "../img/menu/menu8_on.gif" 
f_name[9] = "../img/menu/menu9_on.gif" 
f_name[10] = "../img/menu/menu10_on.gif" 
f_name[11] = "../img/menu/menu11_on.gif" 
f_name[12] = "../img/menu/menu12_on.gif" 
f_name[13] = "../img/menu/menu13_on.gif" 
f_name[14] = "../img/menu/menu14_on.gif" 
f_name[15] = "../img/menu/menu15_on.gif" 

var i 
for(i = 1;f_name.length > i;i++) 
{file[i] = new Image();file[i].src = f_name[i]} 
}