html - input에 배경 이미지 넣기

<script>
function clrImg(obj){obj.style.backgroundImage="";obj.onkeydown=obj.onmousedown=null;}
</script>

<input onkeydown="clrImg(this)" onmousedown="clrImg(this)"
    style="background-image:url(http://jsguide.net/ver2/examples/wow.gif);background-repeat:no-repeat;background-position:center;">