JS n00b preload images problem

[knowj]

I have this Javscript that im using to preload images that rollover but for some reason it seems to do nothing. It would help if it errored :S

<script type="text/javascript">
		<!--
			if (document.images)
				{
					preload_image_object = new Image();
					// set image url
					image_url = new Array();
					image_url[0] = "images/image_1_rollover.jpg";
					image_url[1] = "images/image_2_rollover.jpg";
					image_url[2] = "images/image_3_rollover.jpg";
					image_url[3] = "images/image_4_rollover.jpg";
					image_url[4] = "images/image_5_rollover.jpg";
					image_url[5] = "images/image_6_rollover.jpg";
					image_url[6] = "images/image_7_rollover.jpg";
					image_url[7] = "images/image_8_rollover.jpg";
					image_url[8] = "images/image_9_rollover.jpg";
					image_url[9] = "images/image_10_rollover.jpg";
					image_url[10] = "images/enterflashsiterollover.png";
					image_url[11] = "images/enterhtmlsiterollover.png";
					
					var i = 0;
					for(i=0; i<=9; i++){preload_image_object.src = image_url[i];}
					}
		//-->
		</script>

[vwphillips]

<script type="text/javascript">
		<!--
			if (document.images)
				{
					preload_image_object =[];
					// set image url
					image_url = new Array();
					image_url[0] = "images/image_1_rollover.jpg";
					image_url[1] = "images/image_2_rollover.jpg";
					image_url[2] = "images/image_3_rollover.jpg";
					image_url[3] = "images/image_4_rollover.jpg";
					image_url[4] = "images/image_5_rollover.jpg";
					image_url[5] = "images/image_6_rollover.jpg";
					image_url[6] = "images/image_7_rollover.jpg";
					image_url[7] = "images/image_8_rollover.jpg";
					image_url[8] = "images/image_9_rollover.jpg";
					image_url[9] = "images/image_10_rollover.jpg";
					image_url[10] = "images/enterflashsiterollover.png";
					image_url[11] = "images/enterhtmlsiterollover.png";

					var i = 0;
					for(i=0; i<=9; i++){
                     preload_image_object[i]=new Image();
                     preload_image_object[i].src = image_url[i];}
                   	}
		//-->
		</script>

[knowj]

cheers much appreciated