function _preload(str){

	if(!document.images)
		return;

	if(!str)
		return;

	if(str.length == 0)
		return;

	var i, arr, img;

	// nav
	arr = str.split(",");
	for(i = 0; i < arr.length; i++){
		img = new Image();
		img.src = "images/" + arr[i];
	}


}