Never Use 2 Spaces After A Period

CanI let you in on a secret? Typing two spaces after a period is totally, completely, utterly, and inarguably wrong . And yet people who use two spaces are everywhere, their ugly error crossing every social boundary of class, education, and taste. * You’d expect, for instance, that anyone savvy enough to read Slate would know the proper rules of typing, but you’d be wrong; every third e-mail I get from readers includes the two-space error. (In editing letters for “Dear Farhad,” my occasional tech-advice column, I’ve removed enough extra spaces to fill my forthcoming volume of melancholy epic poetry, The Emptiness Within .) The public relations profession is similarly ignorant; I’ve received press releases and correspondence from the biggest companies in the world that are riddled with extra spaces/ Farhad Manjoo , Slate. More here . H/T: Arpie.

Question: Do you use two spaces after a period in a sentence? And/or: Which punctuation mistake bugs you most?