Class warfare

HTML

<button>Run the script code</button>

<table id="sort_table" class="tablesorter">
<thead>
    <tr>
        <th class="blacktext timesroman_italic">This</th>
        <th class="blacktext timesroman_italic">is a</th>
        <th class="blacktext timesroman_italic">header</th>
        <th class="blacktext timesroman_italic">row</th>
    </tr>
</thead>
<tbody>
    <!-- I WOULD LIKE TO DELETE FROM HERE -->
    <tr class="" valign="middle">
        <td class="bluetext timesroman align_middle">First</td>
        <td class="bluetext timesroman align_middle">blank</td>
        <td class="bluetext timesroman align_middle">class</td>
        <td class="bluetext timesroman align_middle">row</td>
    </tr>
    <!-- TO HERE -->

    <!-- BUT NOT FROM HERE -->
    <tr class="" valign="middle">
        <td class="bluetext timesroman align_middle">second</td>
        <td class="bluetext timesroman align_middle">blank</td>
        <td class="bluetext timesroman align_middle">class</td>
        <td class="bluetext timesroman align_middle">row</td>
    </tr>
    <tr class="someclass" valign="middle">
        <td class="bluetext timesroman align_middle">I gots</td>
        <td class="bluetext timesroman align_middle">me</td>
        <td class="bluetext timesroman align_middle">some</td>
        <td class="bluetext timesroman align_middle">class</td>
    </tr>
    <tr valign="middle">
        <td class="bluetext timesroman align_middle">no</td>
        <td class="bluetext timesroman align_middle">class</td>
        <td class="bluetext timesroman align_middle">attribute</td>
        <td class="bluetext timesroman align_middle">row</td>
    </tr>
    <!-- TO HERE -->
</tbody>
</table>

CSS

tbody tr:not([class]), tbody tr[class=""] {
    background: pink;
}
th {
    background: lightYellow;
}

JavaScript

$("button").click ( function () {
    $('#sort_table tbody tr:not([class!=""]):first').remove ();
} );