Transparent background

[Ishtar]

I would like my template to be transparent for me to add a custom background. But I cant't make it work. In my theme's css I set:

body {
	margin: 0;
	margin-top: 10px;
	font-family: verdana, arial, helvetica, sans-serif;
	font-size: 62.5%;
	color: #999999;
	background-color: #000000;
	background-image: url(../images/pagebg.gif);

Is it right?

and what about tables background? In fact I would like all my templete to be transparent.