table's backround color opacity

hi

im trying to change the opacity of the table's backround color.
i changed this css part trying to make it transparent so i can see the image at the back but whatever i tried nothing changed.anyone know how i can do it?

Code:

td.row1{
 background-color: #232323;
 }
td.row2{
 background-color: #202020;
 }
td.row3{
 background-color: #232323;
 }

This would be the code for opacity (80% in my following example)

Code:

opacity: .8;
filter: alpha(opacity=80);
-moz-opacity: .8;

if you want to make your background color entirely invisible, you can simply use:

Code:

background-color: transparent;