if you want to change event td tag.you can use method of getElementsBytagName.
<table border="1" id="mytable">
<tr><td>
left cell
</td>
<td>
right cell
</td></tr>
<tr><td>left cell</td><td>right cell</td></tr></table>
<a href="javascript
:go()">Change Text</a>
<script>
function go(){
var k=document.getElementsByTagName('table');
for(i=0;i<k.length;i++){
if(k[i].id=="mytable"){
var tbody=k[i].childNodes[0];
for(p=0;p<tbody.childNodes.length;p++){
tr=tbody.childNodes[p];
for(j=0;j<tr.childNodes.length;j++){
tr.childNodes[j].firstChild.nodeValue+="1";
}
}
}
}
}
</script>