So, what is it that you can play around with in order to make changes to your mat sizes? The cellpadding, table widths, and adding or deleting line break codes! Simple? Yes! Can you mess things up? Yes!
How do you protect yourself from making changes and not knowing where to "go" to put it back the way it should be?
Well, make a copy of your page BEFORE you begin -- and work away. Then, if you mess up...you have a backup copy to go to. This is just simple computer smarts...but sometimes a reminder is good!