画像名.lowsrc = URL
<img src="../../images/hana.gif" name="myPic" width="200"
height="175" lowsrc="../../images/hana_02.gif" alt="花の絵">
<script type="text/javascript>
<!--
myURL = document.myPic.lowsrc;
document.write("画像のパスは", myURL);
//-->
</script>