In 2.5 the site description input changed from a textarea to a RTEditor.

The RTEditor produces markup. The site browser listing (other places as well perhaps) is still trimming this description as a string. This means that the description might be trimmed to an unbalanced markup fragment that will will badly affect the rendering of wherever the trimming is happening.

To reproduce, put the following into a site "Customize Site Info Display" into the RTEditor in markup mode (this just happened to work for me).

<h3>Some stuff</h3>
<br />
<table cellspacing="1" cellpadding="1" border="0" align="left" style="width: 301px; height: 62px;">
    <tbody>
        <tr>
            <td>Some tabular data</td>
            <td>Some more tabular data from the same source</td>
        </tr>
    </tbody>
</table>

then log out, go to Gateway > Sites, and search for "Any" sites leaving the Search for: field blank. Any sites listed after the one with the bad description will display incorrectly - in this case all columns shifted to the right.