延迟加载兼容ie,ff

<img src="url(about:blank)" alt="四川" url="lxxz.gif"/>
<script>
	function lazyLoad() {
		var img = document.getElementsByTagName("IMG");
		var URL = "";
		if(-[1,]) {
			URL = img[0].getAttribute("URL");
		} else {
			URL = img[0].url;
		}
		alert(URL);
		img[0].src = URL;
	}
	setTimeout("lazyLoad()", 2000);
</script>

<img src="http://" alt="四川" url="http://t3.baidu.com/it/u=3689044725,3973015029&fm=0&gp=0.jpg" />
<p>1</p><p>2</p><p>3</p><p>4</p><p>5</p>
<p>11</p><p>22</p><p>33</p><p>44</p><p>55</p>
<p>11</p><p>22</p><p>33</p><p>44</p><p>55</p>
<img src="http://" alt="四川" url="http://t3.baidu.com/it/u=3641658168,1981948044&fm=0&gp=0.jpg" />
<p>11</p><p>22</p><p>33</p><p>44</p><p>55</p>
<p>11</p><p>22</p><p>33</p><p>44</p><p>55</p>
<p>11</p><p>22</p><p>33</p><p>44</p><p>55</p>
<img src="http://" alt="四川" url="http://t3.baidu.com/it/u=3578877803,3532663606&fm=0&gp=0.jpg" />
<script>
	function lazyLoad() {
		var img = document.getElementsByTagName("IMG");
		for(var x=0;x<img.length;x++) {
			if (isShow(img[x])) {
				showImg(img[x]);
			}
		}
		setTimeout("lazyLoad()", 10);
	}
	function showImg(targetImg) {
		if (targetImg.src == "http:///") {
			if (-[1,]) {
				targetImg.src = targetImg.getAttribute("URL");
			}	else {
				targetImg.src = targetImg.url;
			}
		}
	}
	function isShow(targetObj) {
		var ref = document.body.scrollTop;
		var asl = document.body.clientHeight;
		var rel = targetObj.offsetTop;
		if(rel-ref<asl && rel-ref > 0) {
			return true;
		}
	}
	lazyLoad();
</script>