This example was found by Dan Landrum at http://www.html.it/articoli/niftycube/index.html

The CSS:

div#nifty {margin: 10px; background: #9BD1FA}
 
b.rtop, b.rbottom {display:block;background: #FFF}
b.rtop b, b.rbottom b {display:block;height: 1px; overflow: hidden; background: #9BD1FA}
 
b.r1{margin: 0 5px}
b.r2{margin: 0 3px}
b.r3{margin: 0 2px}
b.rtop b.r4, b.rbottom b.r4{margin: 0 1px;height: 2px}

The HTML:

<div id="nifty">
<b class="rtop"><b class="r1"></b><b class="r2"></b><b class="r3"></b><b class="r4"></b></b>
<!-- Content Here -->
<b class="rbottom"><b class="r4"></b><b class="r3"></b><b class="r2"></b><b class="r1"></b></b>
</div>