[html] html table cell width for different rows

You can't have cells of arbitrarily different widths, this is generally a standard behaviour of tables from any space, e.g. Excel, otherwise it's no longer a table but just a list of text.

You can however have cells span multiple columns, such as:

<table>
    <tr>
        <td>25</td>
        <td>50</td>
        <td>25</td>
    </tr>
    <tr>
        <td colspan="2">75</td>
        <td>20</td>
    </tr>
</table>

As an aside, you should avoid using style attributes like border and bgcolor and prefer CSS for those.