alguien tan amable

[sirdaiz]

alguien tan amable me podria explicar esto??

text.css

Código HTML:

.box_heading_table                  {}
.box_heading_table .box_heading_td  {background:#3d3d3d url(images/box_heading_c.gif) top repeat-x; padding:1px 10px 1px 15px;}
.box_heading_table .box_heading_td  {color:#ffffff; font-weight:bold; font-size:11px; text-transform:uppercase; font-family:Arial }
 
 
.box_heading_tall_t {background:#3d3d3d url(images/box_heading_t.gif) top repeat-x;}
.box_heading_tall_b {background:#3d3d3d url(images/box_heading_b.gif) bottom repeat-x;}
.box_heading_tall_l {background:#3d3d3d url(images/box_heading_l1.gif)}
.box_heading_tall_r {background:#3d3d3d url(images/box_heading_r1.gif)}
 
 
.box_body_table .box_body_tall_l {background:url(images/box_heading_c.gif) left repeat-y;}
.box_body_table .box_body_tall_r {background:url(images/box_heading_t.gif) right repeat-y;}
.box_body_table .box_body_tall_b {background:url(images/box_heading_t.gif) bottom repeat-x;}
 
.box_body_table .box_body_td {padding:0px;}
 

index.html

Código HTML:

<table cellpadding="0" cellspacing="0" border="0" class="box_heading_table">
   <tr>
              <td><img src="images/box_heading_tl.gif" alt="" border="0"></td>
              <td style="width:100%" class="box_heading_tall_t"></td>
              <td><img src="images/box_heading_tr.gif" alt="" border="0"></td>
   </tr>
   <tr>
              <td class="box_heading_tall_l"><img src="images/box_heading_l.gif" alt="" border="0"></td>
              <td style="width:100%" class="box_heading_td">category</td>
                                            <td class="box_heading_tall_r"><img src="images/box_heading_r.gif" alt="" border="0"></td>
     </tr>
     <tr>
              <td><img src="images/box_heading_bl.gif" alt="" border="0"></td>
              <td style="width:100%" class="box_heading_tall_b"></td>
             <td><img src="images/box_heading_br.gif" alt="" border="0"></td>
      </tr>
</table>
 

Gracias