what version of VS.NET are you using? consider to add this line into the header:
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
我的aspx文件中有<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">拉?
<tr>
<td>
<iframe src="http://msdn.microsoft.com"></iframe>
</td>
</tr>
</table>