Word '07

I added several more rows to an existing table using the tab key. In the column that I've been typing fractions as part of a phrase in each cell of the column that fraction auto changes to the small size. However, the fraction is not auto changing in the cells of the added rows.

1. I do not understand why this would occur simply by adding rows?

2. I cannot figure out how to 'turn back on' the auto shrink feature?

Mark