Hvordan laver man hver anden tabellinie grå

Hej

Hvordan løser jeg det problem at jeg ønsker at lave hver anden linie grå i nedenstående php-udtræk?

------------

<table cellspacing="2" cellpadding="2" width="570">

<tr>
      <td><b>Nummer</b></td>
      <td><b>Mærke</b></td>
      <td><b>Model</b></td>
      <td><b>Type</b></td>
      <td><b>Variant</b></td>
      <td><b>Pris</b></td>
      <td><b>Km</b></td>
     
</tr>
<tr>
<TD colspan="8"><HR width="570%">
</td>
</tr>




<?
if($_GET['up'] == "ja"){
    include("config.php");
    $db = mysql_connect($server, $user, $pass);
    mysql_select_db($database, $db);

$where=array();
    if($_POST['maerke']!='1')
    {
        $where[]="bil_bil.maerke='".$_POST['maerke']."'";
    }
    if($_POST['model']!='1')
    {
        $where[]="bil_bil.model='".$_POST['model']."'";
    }
    if($_POST['type']!='1')
    {
        $where[]="bil_bil.type='".$_POST['type']."'";
    }
    if($_POST['variant']!='1')
    {
        $where[]="bil_bil.variant='".$_POST['variant']."'";
    }

    $foresp = mysql_query("SELECT bil_bil.id, bil_bil.pris, bil_bil.km, bil_farve.farve AS farve1, bil_bil.maerke, bil_bil.model, bil_bil.type, bil_bil.variant, bil_model.model AS model1,  bil_maerke.maerke AS maerke1, bil_type.type AS type1, bil_variant.variant AS variant1
      FROM bil_bil
      LEFT JOIN bil_maerke ON bil_maerke.id = bil_bil.maerke
      LEFT JOIN bil_farve ON bil_farve.id = bil_bil.farve
      LEFT JOIN bil_model ON bil_model.id = bil_bil.model
      LEFT JOIN bil_type ON bil_type.id = bil_bil.type
      LEFT JOIN bil_variant ON bil_variant.id = bil_bil.variant
     

      ".(count($where)?"WHERE ".implode(" AND ",$where):"")."
      ORDER BY bil_bil.maerke desc
    ");

    while ($data = mysql_fetch_array($foresp))
{
    echo "<tr><td><a href='visbil.php?id=".$data['id']."target='_top'>".$data['id']."</a></td><td><div align='left'><a href='visbil.php?id=".$data['id']."target='_top'>".$data['maerke1']."</a></td><td><a href='visbil.php?id=".$data['id']."target='_top'>".$data['model1']."</a></td><td><a href='visbil.php?id=".$data['id']."target='_top'>".$data['type1']."</a></td><td><a href='visbil.php?id=".$data['id']."target='_top'>".$data['variant1']."</a></td><td><div align='right'><a href='visbil.php?id=".$data['id']."target='_top'>".$data['km']."</a>&nbsp;km</div></td><td><div align='right'><a href='visbil.php?id=".$data['id']."target='_top'>".$data['pris']."</a>&nbsp;kr.</div></div></td></tr>";
}
}
?>
</tr>
</table>

<br></center>

</td>
</tr>
</table>