Еще вариант
<script>
window.onload = function () {
var allSp = document.querySelectorAll('tr.Details span');
for (var txt = '', i = 0; i < allSp.length; i++)
txt += allSp[i].innerHTML.replace(/<.*?>/g, '') + ' ';
alert(txt);
}
</script>
<body>
<table>
<tr class="Details" id="1_14" data-id="14" data-currency="1">
<td># 1</td>
<td>
<span class="HiPart">98</span>
<span class="MiddlePart">76</span>
<span class="LowPart">00</span>
</td>
</tr>
</table>
</body>