IE7部分标签(span、input )设置text-indent:-9999px后不在

<div>
<ipunt style="text-indent:-9999px;background-image:url(a.jpg)" >
</div>

<div>
&nbsp;<ipunt style="text-indent:-9999px;background-image:url(a.jpg)" >&nbsp;
</div>

<style>
span{text-indent:-9999px;background-image:url(a.jpg)}
</style>
<div>
&nbsp;
<span>微软雅黑1</span>
<span>微软雅黑2</span>
<span>微软雅黑3</span>
&nbsp;
</div>