Why doesn't this javascript code run ?

[chu2654]

I want when the user points to a picture link, the picture will become another one. But the following code will always have erros: document[...] is null or is not an object. What's the problem ?

<script language="JavaScript" type="text/javascript">
<!--
productoff = new Image;
productoff.src = "./img/product.gif";
productover = new Image;
productover.src = "./img/news.gif";


function replaceImg(oldImg,newImg){
document[oldImg].src = eval(newImg + ".src");
}
//-->

</script>


<td><a href="./product.html" onMouseOver = "replaceImg('productoff','productover')" onMouseOut = "replaceImg('productoff','productover')" ><img src = "./img/product.gif" ></a></td>