.grand {
    width:760px;
    margin:0 0 10px 0;
    padding: 0 0 5px 0;
    border:  solid 1px #8f8fff;
}
.grand h1{
    background:url(../images/fond_h1_article.jpg) repeat-x;
    font-size: 95%;
    margin: auto;
    padding: 0 0 0 3px;
    line-height: 160%;
    color: #000
}
.petit {
    width:245px;
    margin: 0 0 0 5px;
    padding:auto;
    border:  solid 1px #8f8fff;
    float:left;
}
.petit h1{
    background:url(../images/fond_h1_article.jpg) repeat-x;
    font-size: 90%;
    margin: auto;
    padding: 0 0 0 3px;
    line-height: 160%;
    color: #000
}

        echo '<div class="grand">';
        echo '<h1>L\'annuaire</h1>';
        echo '<div class="petit">';
        echo '<h1>Le top 5</h1>';
        //affichage des 5 derniers inscrits
        $req1=mysql_query("select nom from annuaire order by date_ajout desc limit 5") or die (mysql_error());
        while ($res1=mysql_fetch_array($req1)) {
            echo '<p>'.$res1['nom'].'</p>';
            }
        echo '</div>';
        echo '<div class="petit">';
        echo '<h1>Les + visités</h1>';
        //affichage des plus visiter
        $req2=mysql_query("select nom from annuaire order by nb_clic asc limit 5") or die (mysql_error());
        while ($res2=mysql_fetch_array($req2)) {
            echo '<p>'.$res2['nom'].'</p>';
            }
        echo '</div>';
        echo '<div class="petit">';
        echo '<h1>Le top 5 cat&eacute;gorie</h1>';
        echo '</div>';
        echo '</div>';

.grand {
    width:760px;
    margin:0 0 10px 0;
    padding: 0 0 5px 0;
    border:  solid 1px #8f8fff;
    overflow:auto;
}

.grand {
    width:760px;
    margin:0 0 10px 0;
    padding: 0 0 5px 0;
    border:  solid 1px #8f8fff;
    overflow: visible; /* pour IE*/
    height: 1%;
}

html>body .grand { /* pour les autres */
overflow: hidden
}