table background changing on postback

 Hey all --
I have a table whose background I've set to transparent in its CSS class.  In this table is a control with another table containing three cells that have text in them.  Its background is also set to transparent.  Everything works fine when it first loads.  However, on a postback, a image loads in each of the three cells of the control's table.  Does anyone have any ideas why this would happen?   I found a similar posting on this, but the answer didn't work for me.

 thanks,
 kimberly.  (code below)
 
Main code is along the lines of: 
<table class="shadyBar">
        <tr>
            <td>
                <uc1:aControl />
   &nb ...