var mainmenu = new Array( "mainitem1","mainitem2","mainitem3","mainitem4","mainitem5","mainitem6","mainitem7","mainitem8" );
var submenu = new Array( "item1","item2","item3","item4","item5","item6","item7","item8" );
//get id value
function $( id ){
	return document.getElementById( id );
}
//show and hidden the menu
function display_submenu( id ){
	var _id = $( id );
	if( _id.style.display == "none" ){
		_id.style.display = "block";
	} else {
		_id.style.display = "none";
	}
	return false;
}
//entrance program
function mouseover( id ){
	var _sub = id.substring( id.indexOf( "item" ),id.length );
	for( var i = 0; i < submenu.length; i++ ){
		$( submenu[i] ).style.display = "none";
	}
	//display_submenu( _sub );
	$( _sub ).style.display = "block";
}
//effect when the mouse move out
function mouseout( id,event ){}