Thought I'd add to this a potential other solution:
<tr style='visibility:collapse'><td>stuff</td></tr>
I've only tested it on Chrome but putting this on the <tr>
hides the row PLUS all the cells inside the row still contribute to the widths of the columns. I will sometimes make an extra row at the bottom of a table with just some spacers that make it so certain columns can't be less than a certain width, then hide the row using this method. (I know you're supposed to be able to do this with other css but I've never gotten that to work)
Again, I'm in a purely chrome environment so I have no idea how this functions in other browsers.