Pb d'affichage des div entre IE et fox

<div id ="geant">

    <div id="haut">
    </div>

    <div id="gauche">
    </div>

    <div id="milieu">
    </div>

    <div class="clear"></div>

    <div id="bas">
    </div>

</div> 

#geant{width:1024px;}

#haut {background-color: green;height: 115px; width:1024px;}

#gauche {background-color: red; height:538px;width:143px;float:left;}

#milieu {background-color: blue; height:538px; width:871px;float:left;}

#bas {background-color: silver; height:115px; width:1024px;}

.clear{clear: both;}