Non riesco a far visualizzare un'immagine di sfondo su FF e Opera.

Riducendo all'osso il codice, mi trovo con:
CSS:
codice:
html, body {
	margin:0; padding:0;
}

body {
	text-align: center;
	font-family: Verdana, Arial, Helvetica, sans-serif;
}

#container {
	width: 900px;
	text-align: left;
	margin-left: auto;
	margin-right: auto;
	background-image: url(images/bbg.gif);
	background-position: left top;
	background-repeat: repeat-y;
}
#leftbar {
	width: 160px;
	float: left;
}
#rightbar {
	width:160px;
	float:right;
	left:740px;
}

#contents {
	float:left;
	left:160px;
	width: 580px;
}
e HTML
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Test Page</title>
<link href="style.css" rel="stylesheet" type="text/css">
</head>

<body>
  <div id="container">
	  <div id="rightbar">Right bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar textRight bar text Right bar text Right bar text</div>
	  <div id="leftbar">Left bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar textLeft bar textLeft bar textLeft bar text Left bar text</div>
	  <div id="contents">Main contents text</div>
  </div>
</body>
</html>
Risultato: immagine di sfono visualizzata solo su IE!!!
bbg.gif per intenderci è un'immagine larga esattamente 900px e alta 2.