Ага вот-оно идеальное решение)))
Вся фишка в nth-child( )
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1251" />
<title></title>
<script type="text/javascript" src="http://code.jquery.com/jquery-latest.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("table tr>td:nth-child(3)").html("Привет я третий столбец");
});
</script>
</head>
<body>
<table class="table" border="1" cellpadding="0" cellspacing="0">
<tr><td>11</td><td>12</td><td>13</td><td>14</td></tr>
<tr><td>21</td><td>22</td><td>23</td><td>24</td></tr>
<tr><td>31</td><td>32</td><td>33</td><td>34</td></tr>
<tr><td>41</td><td>42</td><td>43</td><td>44</td></tr>
<tr><td>51</td><td>52</td><td>53</td><td>54</td></tr>
</table>
</body>
</html>