owner of dir/files

[M.D. DeWar]

Hello,
A simple question for you in the know unix guys.

I just noticed that when I d/led a program and un-tarred it and set it up
that the directory in the apache web root has
as owner something like 501:www . I also noticed some others that were
mysql:mysql or 500:100 for the user/group.

I am not sure what happens if left that way. Since there is no user/group
for those does it mean the files won't run or be served ?

In my web root should all directories and files be nobody:nobody  ?

what if some are root:wheel ?

Thanks
Newbie Mark