[jQuery] Interacting with TR an TD

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Hello all, I'm getting used to the excellent jQuery library and I need
some help of more experienced programmers. I have this simple table:

<table class="table">
        <tr>
                <td>content</td>
                <td>content</td>
                <td>content</td>
        </tr>
        <tr>
                <td>&nbsp;</td>
                <td>&nbsp;</td>
                <td>&nbsp;</td>
        </tr>
        <tr>
                <td>content</td>
                <td>content</td>
                <td>content</td>
        </tr>
</table>

What I need is to add a class to the TRs that have children TDs that
have &nbsp; inside (and ONLY &nbsp;)... I'm having problems because
&nbps; is not text, it's html code...

Thanks in advance!