okkei io ho fatto così:

body {
margin:0px;
padding:0px;
font-family:Trebuchet, arial, helvetica;
font-size:11px;
color:#A29A9A;
background-color:white;
background-image:url(fondino1.jpg);
background-repeat:repeat;
height: 100%;
width: 100%;
text-align: center;
}

#contenitore {
position:relative;
margin:auto;
margin-top:0;
font-family:Trebuchet, arial, helvetica;
font-size:11px;
color:#A29A9A;
background-color:white;
height: 100%;
width: 740px;
text-align: left;
}