je vous jette en vrac mon .css au cas ou :
body {
margin: 0;
padding: 0;
}
#global {
position:absolute;
left: 50%;
width: 750px;
margin-left: -375px;
height: 550px;
border: 2px solid #333;
background: #0033CC;
}
#entete {
top : 0px;
left : 0px;
width: 100%;
height: 70px;
}
#menu {
position: absolute;
top: 71px;
left: 0;
z-index: 100;
width: 100%;
}
#frame {
margin-left: 0px;
top : 90px;
left : 0px;
width: 750px;
height: 450px;
overflow: auto;
}
#logo {
top : 0px;
left : 0px;
margin-left: 0px;
width: 100px;
height: 60px;
}
dl, dt, dd, ul, li {
margin: 0;
padding: 0;
list-style-type: none;
}
#menu dl {
float: left;
width: 6em;
margin: 0 1px;
}
#menu dt {
color: #000099;
cursor: pointer;
text-align: center;
width: auto;
font-weight: bold;
background: #FFFFFF;
border: 1px solid gray;
}
#menu dd {
border: 1px solid gray;
}
#menu li {
text-align: center;
background: #FFFFFF;
}
#menu li a, #menu dt a {
color: #000099;
text-decoration: none;
display: list-item;
height: 100%;
border: 0 none;
}
#menu li a:hover, #menu li a:focus, #menu dt a:hover, #menu dt a:focus {
background: #FFFF99;
}
#entetetexte {
position: absolute;
top: 20px;
left: 350px;
width: 400px;
color: #FFFF00;
font-style: italic;
font-weight: bold;
font-size: 15pt;
}
#affiche {
position: absolute;
top: 50px;
left: 100px;
width: 500px;
height: auto;
z-index: 1;
padding: 10px;
border: 10px ridge #FFFF00;
color: #FFFF00;
background-image: url(http://sensol.club.fr/essai/images/background.jpg)
}