A border of 2px (1px width on each side) corresponds to a 5%. Therefore, with a 2px border — for example, as in Wikipedia:Tutorial (Wrap-up and more info) — the width needs to be 95% for the table to fit within the screen. Since it's possible that some tables might not have a border, correction on the individual page could be made after substitution. Another way to create a two column table is like this:
{{col-begin|width=95%}}
|-
|
Left column
|
Right column
|}
