Just a bit more background:
The reason the prompt is available is that silently changing things in
the Normal.dot template is a favorite trick of macro viruses. You
should leave the option turned on at all times. If you get the prompt
and you don't know what changed, you should answer No and the changes
won't be saved.
There are a few problems with that scenario. For one thing, many users
have no idea what Normal.dot is, let alone what they might have done
during an editing session to change it. (Some examples are: adding or
modifying a style and checking the "Add to template" box in the
dialog; making a new AutoCorrect or AutoText entry; creating or
modifying a toolbar button or a keyboard shortcut; or changing a font
setting in the Format > Font dialog and clicking the Default button.)
Even if you're aware of the things that can change the template, you
may not remember everything you did during a long session.
Finally -- thankfully! -- the #$% hackers and script kiddies seem to
have found that it's easier or more satisfyingly destructive to make
"regular" viruses rather than macro viruses, so there are fewer macro
attacks than there used to be. Also, the major antivirus apps are
pretty good at spotting infected documents and quarantining them
before they can even be opened.
One other thing: if the document is based on a template other than
Normal.dot and you did something that changed that template (for
example, adding a custom toolbar), you'll be prompted to save the
template regardless of the setting of the option for Normal.dot. It's
just the same as the prompt you get if you edit a document and then
click Close without saving.
