how to control distance with CSS in span tag

hello, I made up a span tag to make image links in a row. But I cannot control distance between a image and another image. Please advise me how to control with CSS. browsing enviroment I.E and FireFox

++main.html++
<table width="600">
<tr>
<td>
<span class="footer_img1">
<a href="a.html"><img src="a.jpg" border="0"><a>
<!-- I'd like to change the distance here-->
<a href="b.html"><img src="b.jpg" border="0"><a>
<!-- I'd like to change the distance here-->
<a href="c.html"><img src="c.jpg" border="0"><a>
<!-- I'd like to change the distance here-->
<a href="d.html"><img src="d.jpg" border="0"><a>
<!-- I'd like to change the distance here-->
<a href="e.html"><img src="e.jpg" border="0"><a>
</span>
</td>
</tr>
</table>

++detail.css++
CSS code belows

.footer_img1 {
      margin-left: 11px;
      height: 20px;
      width: 143px;
}

B.W, portal123