function drop(num_menu){
for (i=1; i<3; i++) {
 var menuhidde="box_"+i;
 document.getElementById(menuhidde).style.visibility='hidden';
}
var menushow= "box_"+num_menu;
 document.getElementById(menushow).style.visibility='hidden';
if(document.getElementById(menushow).style.visibility=='hidden'){
 document.getElementById(menushow).style.visibility='visible';
}
else
{
document.getElementById(menushow).style.visibility='hidden';
}
}
function effdrop(){
for (i=1; i<3; i++) {
 var menuhidde="box_"+i;
 document.getElementById(menuhidde).style.visibility='hidden';
}
}