demo.htm<script language=javascript>
var newWindow;
newWindow = window.open("2.htm","","width=200;height=300");
</script>
<input type=button onclick="addRow(1)" value="addRow">
<script>
function addRow(s)
{
    var tr1 = newWindow.dTable.insertRow(s)
    var td1 = tr1.insertCell();
    td1.innerText = "Cell1";
    var td2 = tr1.insertCell();
    td2.innerText = "Cell2"
}
</script>
2.htm<table id="dTable" name="dTable">
<tr>
<td>1</td>
<td>2</td>
</tr>
</table>