css round corners

I have three images. One for the left, one for the right and one for the middle. This is what i have:

 <style type="text/css">
 img {border:0}

.bl {background: url(images/backer_left.gif) top left no-repeat; height:47px; }
.br {background: url(images/backer_right.gif) top right no-repeat; height:47px;}
.tr {background: url(images/backer_alt.gif) ; margin:0 4px 0 4px; font-size:12px; height:47px;}
.trText { padding:10px; } 
.clear { clear:both; }
</style>
<div class="bl">
  <div class="br">
    <div class="tr">
        <div class="trText">lay lay lomm</div>
    </div>
   </div>
</div>  
<div class="clear">&nbsp;</div>  

i cannot see the left and the right images. just the repeating backer_alt.gif. what am i doing wrong? thx

edited this version works:

 <style type="text/css">
 img {border:0}

 .bl {background: url(images/backer_left.gif) top开发者_如何学Go left no-repeat; height:47px; }
 .br {background: url(images/backer_right.gif) top right no-repeat; height:47px;}
 .tr {background: url(images/backer_alt.gif) ; margin:0 4px 0 4px; font-size:12px; height:47px;}
   .trText { padding:10px; } 
 .clear { clear:both; }
 </style>
<div class="bl">
    <div class="br">
        <div class="tr">
            <div class="trText">lay lay lomm</div>
        </div>
    </div>
 </div>  
 <div class="clear">&nbsp;</div>  

Try setting .tr’s margin to 10px instead of its padding. You also probably need to set the background-position on .br to top right so it appears in the correct place.

As noah says, adding the correct margin left & right to the .tr, depending corner width, will make it appears:

.bl {background: url(images/backer_left.gif) no-repeat left top; }
.br {background: url(images/backer_right.gif) no-repeat right top; }
.tr {background: url(images/backer_alt.gif) repeat-x; margin:0 10px; padding:10 0; }