preLoadImgs

function preLoadImgs() {
	var imgsUrl = [
		'../qhome/img/progress_1.png','../qhome/img/progress_1_1.png',
		'../qhome/img/progress_2.png','../qhome/img/progress_3.png',
		'../qhome/img/progress_4.png'
	];
	for(var i in imgsUrl) {
		preLoadImg(imgsUrl[i]);
	}
}

function preLoadImg(url) { 
  var img = new Image(); 
  img.src = url; 
}