To expand on Colum's advice: the HTML default protocol is to
appropriate as much space as is needed (in each column) to present
the longest string without spaces, starting with column 1 and
progressing through each column. That is, even if you've set column
1 to only be 12% of the total table width, it will "take" more when
presented with a word like "MyExtremelyLongSystemParameter," or
some such.
Additional good practice is to keep the table to 3-4 columns
max. Often, some columnar content can be easily added in one of the
other columns as an extra block with a bolded label. This can also
bring some important content closer to the left margin, instead of
being "way out there" in column 8, for example.
Other options are to keep these tables in a separate,
landscaped Word or Excel document, which which can be more easily
viewed and printed.
Good luck,
Leon