Well, I'm not usually one to just give away code - I much prefer to give directions and have people figure it out - but since this is something that I had to figure out instead of just reciting an answer, I'll let you off this time for feedback purposes. ;)
The below method will only work reliably across the major browsers when in standards-compliant mode, so I hope you're using XHTML 1.0 strict or 1.1. It is not the only method, but only the one that I prefer. I went with an unordered list for the semantich value and also to take advantage of the block-level display of the <li> elements. Because block level elements are automatically preceded and followed by line breaks, I used negative margins to position them on the same line. This allowed me to avoid the use of the float property which separates content from the normal document flow. 0 and auto margins were also used to position the elements horizontally: 0 left margin with auto right to position on far left, auto left and right to center, and 0 right with auto left to position on far right. Each <li> element must have an absolute width, or the auto margin will fail to calculate. The line height of each <li> element was set to match the height of their content box to better center the text vertically.
Below is the CSS I used with the accompanying HTML. It works consistently among Fx 1.x, IE 6.x, and Opera 9.00. If you're curious about earlier versions, I'm afraid you'll have to test them yourself.
body { margin:0; }
#footer {
width:100%;
margin:0;
padding:0;
list-style-type:none;
border-top:solid 10px rgb(207,220,230);
border-bottom:solid 10px rgb(207,220,230);
background-color:rgb(48,130,191);
}
#footer li {
font-size:10pt;
font-family:verdana,sans-serif;
color:white;
height:25px;
line-height:25px;
text-align:center;
}
#footer li a { color:rgb(255,255,255); text-decoration:none; }
#footer li a:hover { color:rgb(207,220,230); }
#footer .copyright { width:250px; margin:0 auto 0 0; }
#footer .footnav { width:300px; margin:-25px auto 0; }
#footer .designer { width:250px; margin:-25px 0 0 auto; }
<ul id="footer">
<!-- Left Aligned -->
<li class="copyright">
Copyright © 2006 <a href="http://mindlesstrio.com">Mindless Trio</a>
</li>
<!-- Center Aligned -->
<li class="footnav">
<a href="http://">Site Map</a> |
<a href="http://">Terms of Use</a> |
<a href="http://">Contact Us</a>
</li>
<!-- Right Aligned -->
<li class="designer">
Design by <a href="http://grungyart.com">Melicbot Entertainment</a>
</li>
</ul>
Here is a sample (http://jfweb.fastmail.fm/3align/navbar_test.htm) that I've uploaded.