How many spaces should be left after a period or other concluding mark of punctuation?

First, they tell me Pluto is not a real planet. Then, I find out the brontosaurus isn’t real. And now this. My entire primary school education is turning out to be a complete sham.

graceinsmallthings: thebluehour:

My world was turned upside-down when an associate in publishing told me that the trend is no longer two spaces after a period and soon it will become a rule.  Schools are now teaching only one period as well. I want to go lay down in a dark room with a cold washcloth over my eyes.

Ever since J-School, I’ve cringed whenever I see two spaces after a period. That rule was thrown out the window the second I left high school.