This play with table-layout:fixed; and applying the width to colgroup or col element. Firefox only recongize the width if it is applied on col element!

On a perfect browser, both tables should look the same

colgroup
300 px width is applied to the first colgroup element
Very long? # $
col
Each colgroup has an additional col element. The first col element is applied the 300 px width
Very long? # $