ho risolto cosi leggendo questo articolo:
http://css.html.it/guide/lezione/64/...ma-del-footer/


html,body{margin: 0;padding:0;height:100%;}
body{font-family: Verdana, Geneva, Arial, Helvetica, sans-serif;;font-size: 76%;text-align: center;background-color: #ede6d6;}
div#container{position:relative; width: 956px; height: 100%;margin: 0 auto;
text-align: left; background-color:#85a9d9;border-right: 1px solid #052754;border-left: 1px solid #052754;}
body>div#container{height:auto;min-height:100%}
div#footer{position: absolute;bottom:0; width: 100%; height:180px;}



div#footer{
background-image: url(../img/bg-tour.jpg);
background-repeat: repeat-y;
background-position: bottom center;
}
div#content{
padding: 0em 0em 180px 0em;
width:940px;
margin-left:auto;
margin-right:auto;
margin-top:0px;
margin-bottom:0px;
}

<div id="container">
<div id="content">
<div style="background-color:#c5d2e8">
<h2 style="margin:0px;">spazio contenuti</h2>


</p>


</p>


</p>


</p>


</p>


</p>


</p>


</p>


</p>


</p>


xxx</p>
</div>
</div>
<div id="footer"></div>
</div>