I am not sure if the div tag is ok for XHTML 1.0 Strict Specification. The follow code is happy in the transitional spec...
Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Untitled Page</title>
</head>
<body>
<p>Hi there</p>
<div style="text-align: right">
<table border="1px" width="500" style="">
<tr>
<td align="left" width="250" style="height: 23px"> Cell One</td>
<td align="left" width="250" style="height: 23px"> Cell Two</td>
</tr>
<tr>
<td align="left" width="250" style="height: 23px"> Cell Three</td>
<td align="left" width="250" style="height: 23px"> Cell Four</td>
</tr>
</table>
</div>
<p>How are things going</p>
</body>
</html>