as wiz said, it's that standards have changed, not that the people who have always done it with two spaces were wrong -- unless they're keying to today's standards. i've been in documentation most of my adult life, and think it was in the early 90s when this standard changed. someone will, i'm sure, correct that for me. anyway, what that means is that for those of us who are "old" and have been in that industry for any amount of time, typing with two spaces after a period is far more natural, and we generally have to remind ourselves to change it to one. or, in my case? i just do an edit/replace. ;-)