body
{
   background-image: url("grande-ourse.jpg");
   background-attachment: fixed;  /* Le fond restera fixe */
   background-repeat: no-repeat; /* Le fond ne se répètera pas */
   background-color: black;
   background-position: center;
   font-size: 16px;
}
#entete
{  
   width: 760px; 
   height: 100px;
   background-image: url("titre.png");
   background-repeat: no-repeat;
   margin:auto;
   top:0px;
}
address a
{
   display:block;
   text-align: center;
   color: yellow;
   position:fixed;
   left:10px;
   bottom:2%;      
}
#menu
{
   position:fixed;
   left:1px;
   top:30%;
}
#menu a
{
   display: block;   /* devient un bloc ... donc propriétés de blocs appliquées */
   width:200px;
   height:50px;
   background-image:url("bouton.png");
   text-align: center;
   text-decoration: none ;
   background-position: 0px -5px;
   background-repeat: no-repeat;
}
#menu li
{
   list-style-type: none;  

}
#corps
{
   width: 500px; /* On a indiqué une largeur (obligatoire) */
   padding: 12px;
   margin: auto; /* On peut donc demander un block centré avec "auto" */
   margin-top: 30px;
   color: yellow; /* texte de la page */
}
h1
{
   width: 600px; 
   height: 35px;
   background-image: url("Hdegrade.png");
   border: thin gray ridge;
   background-repeat: repeat-y;
   font-size: 150%; 
   font-style: italic;
   text-indent: 10px;
   margin-top: 30px;
   margin-bottom: 30px; 
}
h2
{
   color: fuchsia;
   font-size: 125%;
   font-style: italic;
   text-decoration: underline;
}
strong
{
   font-style: italic;
   color: fuchsia;
}
em
{
   font-style: italic;
   color: aqua;
}
.cadre
{
   border: 1px solid white;
   padding: 10px;
}

.legende
{
   display : block;
   width:460px;
   margin:auto; 
   font-style: italic;
   color: lime;
   border: none;
   margin-top:1px;
   padding:5px;
   padding-left:50px;
}
.theoreme
{
   display : block;
   width:400px;
   margin:auto;
   font-style: italic;
   color: lime;
   border: 1px solid gray;
   padding:5px;
   padding-left:20px;
}