I recently learned that it is no longer legit to type two spaces after the punctuation mark ending a sentence. That was a rule we were taught back when type sets were differently arranged than they are now. Way back when the early typewriters were being made, each letter had the same amount of space assigned to it. Thus an "i" would have more space between it and surrounding letters than say, a "w." To compensate for this slight difference in letter spacing, two empty spaces were required for easier visual clarity at the end of a sentence. No more. All modern type uses the same amount of space between letters, so the extra space after the end of a sentence is no longer required. I just found this out the other day and made the switch. I'll bet I'm the last to do this!