Added a copy of Firebug Lite for debugging purposes. License is uncertain but being treated as MPL. (If is is not MPL then it is under something more permissive that permits relicensing anyway)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>{#table_dlg.merge_cells_title}</title>
<script type="text/javascript" src="../../tiny_mce_popup.js"></script>
<script type="text/javascript" src="../../utils/mctabs.js"></script>
<script type="text/javascript" src="../../utils/validate.js"></script>
<script type="text/javascript" src="js/merge_cells.js"></script>
<base target="_self" />
</head>
<body style="margin: 8px" style="display: none">
<form onsubmit="insertTable();return false;" action="#">
<fieldset>
<legend>{#table_dlg.merge_cells_title}</legend>
<table border="0" cellpadding="0" cellspacing="3" width="100%">
<tr>
<td>{#table_dlg.cols}:</td>
<td align="right"><input type="text" name="numcols" value="" class="number min1" style="width: 30px" /></td>
</tr>
<tr>
<td>{#table_dlg.rows}:</td>
<td align="right"><input type="text" name="numrows" value="" class="number min1" style="width: 30px" /></td>
</tr>
</table>
</fieldset>
<div class="mceActionPanel">
<div style="float: left">
<input type="button" id="insert" name="insert" value="{#update}" onclick="mergeCells();" />
</div>
<div style="float: right">
<input type="button" id="cancel" name="cancel" value="{#cancel}" onclick="tinyMCEPopup.close();" />
</div>
</div>
</form>
</body>
</html>