Ajax :: Can't Display A Table Row

I'm trying to click on a link and via Ajax, get a table row to display updated data. I have it all working except it displays at the top of the table instead of inside the table at the desired row. For now, I'm just trying to add a simple table row using:

<TR><TD>test</TD></TR>

Here is my table code:

<TABLE>
<TR><TD>one</TD></TR>
<TR><TD>two</TD></TR>
<span id="id_row3"></span>
</TABLE>

So when I click on my link to execute the ajax code, I expect to see a table row inserted with the text "four" but "four" displays at the top of the web page, above the table itself. How can I get the new row to insert at the id_row3 tag?