}
ul li{ padding: 0px; margin:0 1px 0 0; list-style:none; display:inline; float:left; }
ul li a{ display: inline-block; width: 150px; padding:0 0 5px 0; white-space:nowrap; text-align:center; text-decoration:none;color:#fff; text-shadow:0.1em 0.1em 0.3em black;text-transform:lowercase }
ul li a:hover { color:#fff; text-shadow:0.1em 0.1em 0.3em black }
ul li a span { display:inline-block; height:0px; overflow:hidden; }
ul li a strong { font-size:14px; text-transform:uppercase; padding-top:5px; display:block;}
ul li a.blue { background: url(images/1_2.png) bottom center no-repeat ; }
ul li a.red { background: url(images/5.png) bottom center no-repeat; }
ul li a.orange { background: url(images/2.png) bottom center no-repeat; }
ul li a.green { background: url(images/4.png) bottom center no-repeat; }
ul li a.black { background: url(images/3.png) bottom center no-repeat; }
.clear { clear:both; }
#content { padding:150px 10px 0; width:750px;}
body {font-family:"Lucida Sans Unicode", "Lucida Grande", sans-serif; font-size:11px; color:#333;}
Может задать !important ??? типа:
ul li a.black { background: url(images/3.png) bottom center no-repeat !important; }