How DO u make Custom Cell Backgrounds?

[gforce75]

I'm trying to make custom cell backgrounds, but they all just produce that generic color. Putting html in the title or descrpition does nothing, so how do i do it? i'm stumped :)

[Velocd]

<style type="text/css">
.custombg {
background-image: url(gradient.gif);
background-color: black;
background-position: top left;
background-repeat: repeat-x;
}
</style>

<td class="custombg"></td>

Like this?