Adding a border will move the content down_html/css_WEB-ITnose

When there was no border, the content inside just filled the div.
But after adding the border, the content inside was offset by half of the foot height!
I tested it and it was (margin- top:15px;
border-bottom:1px;) There is a problem here, please tell me how to modify it!
#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;
}

Reply to discussion (Solution)

<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>