varia le altezze a piacimento

codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="it" xml:lang="it">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
        <title>xhtml 1.0</title>
     
        <style>
            body {
                text-align: center;
            }
            #cnt {
                text-align: left;
                margin: 0 auto;
                width   : 900px;
            }
        
            #header {
                height  : auto !important;
                height  : 60px;
                min-height : 60px;
                background  : #cfc;
            }
            
            #main {
                height  : auto !important;
                height  : 400px;
                min-height : 400px;
                background  : #cca;
            }
            
            #footer {
                height      : auto; 
                overflow    : hidden;
                /*** assegna qui un background per simulare le altezze uguali dei tre blocchi ***/
            }
            
            
            #footer div {
                width       : 300px;
                float       : left;
                display     : inline;
                height      : auto !important;
                height      : 100px;
                min-height  : 100px;
                background  : #ccf;
            }
            
        
        </style>

    </head>

<body>

    <div id="cnt">
    
        <div id="header">min height: 60px;</div>
    
        <div id="main">min height: 400px;</div>
    

        <div id="footer">
            <div>Blocco1</div>
            <div>Blocco2</div>
            <div>Blocco3</div>
        </div>

    </div>

</body>
</html>
Ciauz