Why you should never, ever use two spaces after a period.

Besides, the argument in favor of two spaces isn't any less arbitrary. Samantha Jacobs, a reading and journalism teacher at Norwood High School in Norwood, Col., told me that she requires her students to use two spaces after a period instead of one, even though she acknowledges that style manuals no longer favor that approach. Why? Because that's what she's used to. "Primarily, I base the spacing on the way I learned," she wrote me in an e-mail glutted with extra spaces.

Several other teachers gave me the same explanation for pushing two spaces on their students. But if you think about, that's a pretty backward approach: The only reason today's teachers learned to use two spaces is because their teachers were in the grip of old-school technology. We would never accept teachers pushing other outmoded ideas on kids because that's what was popular back when they were in school. The same should go for typing. So, kids, if your teachers force you to use two spaces, send them a link to this article. Use this as your subject line: "If you type two spaces after a period, you're doing it wrong."

Correction, Jan. 18, 2011: This article originally asserted that—in a series of e-mails described as "overwrought, self-important, and dorky"—WikiLeaks founder Julian Assange used two spaces after every period. Assange actually used a monospace font, which made the text of his e-mails appear loose and uneven. (Return to the corrected sentence.)

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