Javascript recuperation valeur dans une page

function recup()
{
gauche=parent.document.getElementById('frameressource').Document;
td=gauche.getElementsByTagName('td');
contenu=td[10].firstChild.data;
alert(contenu);
}

<iframe name="frameressource" id="frameressource" src="http://www.commentcamarche.net" style="position: relative;" height="0%" width="100%"></iframe>

<img style="width: 13px; height: 15px;" onclick="recup();" alt="" src="update.png">

function test22(num22)
{
if ( document.all('frameressource').readyState == 'complete' )
{ document.all('boutonressource').disabled = false ; }
else if ( num22 < 30 )
{
window.setTimeout("test22("+(num22+1)+")", 1000);
}
}

function entreeNDI() 
{ 
if (window.event.type == "keypress" & window.event.keyCode == 13) 
{ 
NDI(); 
} 
}
function NDI()
{
desactiverboutonndi();
if(document.Feuille.ndi.value.match (/^[0-9]{10}$/))
{
}
else
{alert("NDI saisie non valide"); exit();}
desactiverboutonndi();
if (Feuille.ndi.value != "")
{
document.all('frameressource').src='http://xxx/index.php?app=xxx&ndi='+Feuille.ndi.value;
window.setTimeout("test22(0)", 1000);
reduireframe();
frameencours('frameblanc');
}
}

function reduireframe()
{
document.all('frameblanc').height = "0%" ;
document.all('frameressource').height = "0%" ;
}

function desactiverboutonndi()
{ 
document.all('boutonressource').disabled = true ;
}

function frameencours(xx)
{
document.all(xx).height = "100%" ;
}

<form name="Feuille">
<table style="width: 971px; margin-left: 0px;" border="0">
<tbody>
<tr><td style="width: 127px;">

<input name="ndi" maxlength="10" style="width: 110px;" onkeypress="entreeNDI();" type=" text=">

<input name="boutonressource" value="Ressource" class="bt" onclick="reduireframe();frameencours('frameressource');" disabled="true" style="width: 100px;" type="button">

<iframe name="frameressource" id="frameressource" src="" style="position: relative;" height="0%" width="100%"></iframe>
</tbody></table></form>