how do they use "tilesets" to set buttons?

[Lynne]

If you look at the css for the stats which is the box with the arrow thingie in the very left side - 4th down, it looks something like this:

.foro_stats {
...background:transparent url(/themes/revolution/imagenes/general/sprite_forums_rev_blue.png) no-repeat scroll 0 -284px;
height:48px;
width:144px;
}

So, they start at position 0 (x-direction) -284px (y-direction) and then from that point, the image is 48px height and 144px wide.