通过事件改变图片,该怎么解决

通过事件改变图片
<script   language=javascript>
function   chuli()
{
document.getElementByName( "qian1 ").src= "sTDButton.jpg ";
}
</script>


下面是图
<img   border= "0 "   id= "qian1 "   name= "qian1 "   onclick= "Chuli() "     onmouseover= "nereidFade(this,100,1,5) "   style= "FILTER:   alpha(opacity=0) "
onmouseout= "nereidFade(this,0,1,5) "   title= "世代服务网 "   src= "sTDButton.jpg "width= "96 "   height= "32 "   runat= "server ">

怎么老是提示找不到对象啊   ？？？？？？？这是怎么回事啊？？？
请高手指点

------解决方案--------------------------------------------------------
.getElementsByName
------解决方案--------------------------------------------------------
注意大小写