Tryit Editor v1.4

<html>
<head>
<script type="text/javascript">
function changeContent()
{
var x=document.getElementById('myTable').rows[0].cells;
x[0].innerHTML="NEW CONTENT";
}
</script>
</head>

<body>
<table id="myTable" border="1">
<tr>
<td>Row1 cell1</td>
<td>Row1 cell2</td>
</tr>
<tr>
<td>Row2 cell1</td>
<td>Row2 cell2</td>
</tr>
<tr>
<td>Row3 cell1</td>
<td>Row3 cell2</td>
</tr>
</table>
<form>
<input type="button" onclick="changeContent()" value="Change content">
</form>
</body>

</html>

Your Result:

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