function enTeteGD()
{
	   if (screen.width <= 640) return 'images/degrade/degradegd640.gif';
   else if (screen.width <= 800) return 'images/degrade/degradegd800.gif';
   else if (screen.width <= 1024) return 'images/degrade/degradegd1024.gif';
   else return 'images/degrade/degradegd1280.gif';
}
function enTeteDG()
{
   if (screen.width <= 640) return 'images/degrade/degradedg640.gif';
   else if (screen.width <= 800) return 'images/degrade/degradedg800.gif';
   else if (screen.width <= 1024) return 'images/degrade/degradedg1024.gif';
   else return 'images/degrade/degradedg1280.gif';
}
function tail1 ()
{
  if (screen.width <= 800) return '77';
  else return '80';
}
function tail2 ()
{
  if (screen.width <= 800) return '23';
  else return '20';
}

var chaine = '<table width="100%" border="0" background="' + enTeteDG() + '">';
chaine += '  <tr>';
chaine += '    <td width="' + tail1() + '%">&nbsp;</td>';
chaine += '    <td width="' + tail2() + '%" class="titrelien">Bienvenue sur notre site</td>';
chaine += '  </tr>';
chaine += '</table>';
document.write(chaine);