增加了边框，内容就下移
原本没边框的时，里面的内容刚好撑满div，
但是加了边框后，里面的内容就偏移了foot高度的一半!
  我测试了下，是（margin-top:15px;
border-bottom:1px;）这里出问题，请问该如何修改！
#foot{
width:100%;
height:43px;
margin-top:15px;
border-bottom:1px;
border-bottom-style:solid;
border-top:1px;
border-top-style:solid;
background-color:#996699;
}
.zi{
text-align:center;
color:#646464;
}

<div id="foot">
<p class="zi">Copyright @2006 Your Company | All rights reserved<br>
Design by <a href="ss.html">Gerhard Studios</a> | <a href="ss.html">W3C XHTML 1.1</a> | <a href="ss.html">W3C CSS 2.0</a>
</p>
</div>

------解决方案--------------------

HTML code

<div id="foot">
        <div class="zi">
            Copyright @2006 Your Company | All rights reserved<br>
            Design by <a href="ss.html">Gerhard Studios</a> | <a href="ss.html">W3C XHTML 1.1</a>
            | <a href="ss.html">W3C CSS 2.0</a>
        </div>
    </div>