I have a table according to below. The second row has defined three columns, one with colspan=8 and the others with colspan=1. Still, the cells are not stretched according to the colspan, the "width" are a little bit more for second cell and widest for the third.
<table class="floating simpletable">
<tbody>
<tr><td colspan="10">1st row</td></tr>
<tr><td colspan="8">Column 1 -> Least wide</td><td colspan="1">2nd</td><td colspan="1">3rd</td></tr>
<tr><td colspan="10">3rd row</td></tr>
<tr><td colspan="1">1st cell</td><td colspan="9">4th row</td></tr>
</tbody>
</table>
What's the problem and how to fix it?
The widths of cells depend on cell contents, HTML and CSS settings for widths, browser, and possibly phase of the moon. The colspan attribute just specifies how many columns (hence, how many slots in the grid for the table) a cell occupies.
If you see the last cell of row 2 as the widest, then the reason is probably that it has most contents (or there is a width setting for it). Your demo code does not demonstrate such behavior.
If you don’t want the column widths adjust to the size requirements of cells, set the widths explicitly in CSS (or in HTML). Before this, it is best to remove all unnecessary complications from the table structure. If your demo code reflects the entire structure, then columns 2 through 8 are an unnecessary division, i.e. they could be turned to a single column. Demonstration (with poor-style pixel widths just for definiteness):
<table class="floating simpletable" border>
<col width=100><col width=100><col width=100>
<tbody>
<tr><td colspan="4">1st row</td></tr>
<tr><td colspan="2">span 1</td><td>span 2</td><td>span 3 </td></tr>
<tr><td colspan="4">3rd row</td></tr>
<tr><td>span</td><td colspan="3">other span</td></tr>
</tbody>
</table>
Without a rewrite like this, I’m afraid your table violates the table model of HTML, as currently there is no cell that starts in column 3 or column 4 or...