<!DOCTYPE html>
<html>
<head>
<script>
function changeContent(id, row, cell, content) {
var x = document.getElementById(id).rows[row].cells;
x[cell].innerHTML = 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>
<p>
<input type="button" onclick="changeContent('myTable', 0, 0, 'Hello')" value="Change content">
</p>
</body>
</html>