Back in the early days of high school or junior high, I learned to put two spaces after the period at the end a sentence when typing.  I've been doing this ever since.  I've noticed that I'm the only person on earth who does this.  I figured everyone else was wrong, as is usually the case.  But it turns out that it's an ongoing debate.  Basically, the old way of doing things was to put two spaces after the period.  This practice began with typewriters and fixed-width fonts (like Courier), where every letter takes up the same amount of horizontal space on the page.  It was straining on the eyes to read long documents where sentences weren't separated by more than one space, so the extra space was added to make reading easier.  This "old school" approach was handed down and continued by typing teachers, most of whom are old ladies.  But since the advent of proportionally-spaced fonts (like Times New Roman and pretty much everything else), the extra spaces seemed unnecessary to most people.  Also, the introduction of the interweb and HTML made the double-space even more obsolete because HTML only shows one space, whether you put two or seventeen.  But no matter what the current standard is or what's commonly accepted, I'm sticking with my way of doing things because it's arguably the best way of doing things. 

More info here, here, and here. #language