ToolTips and Tables -- how can I have tooltips on the cells of a column?

I could use your help.  I need to add tooltips to each column of an
HTML table, for the entire column of cells.  I want to add a single
element to the table, and have that one element represent the tooltip
for all the cells in the column.

I'm doing the brute-force method right now of adding a tooltip to every
<td> in the table.  The problem there is that the HTML is ballooning in
size as a result (see an example below).

Any ideas, examples or help on this?

        <tbody>
          <tr>
            <td class="bluedata" title="Column 1 ToolTip"> Row 1</td>
            <td class="yellowdata" title="Column 2 ToolTip"> Row 1</td>
            <td class="bluedata" title="Column 3 ToolTip"> Row 1</td>
          </tr>
          <tr>
            <td class="bluedata" title="Column 1 ToolTip"> Row 2</td>
            <td class="yellowdata" title="Column 2 ToolTip"> Row 2</td>
            <td class="bluedata" title="Column 3 ToolTip"> Row 2</td>
          </tr>
          .......
          <tr>
            <td class="bluedata" title="Column 1 ToolTip"> Row 140</td>
            <td class="yellowdata" title="Column 2 ToolTip"> Row
140</td>
            <td class="bluedata" title="Column 3 ToolTip"> Row 140</td>
          </tr>

Thanks,
Frank