From James Snider: If you put two spaces after a period in a sentence, it tells me that you learned to type on a typewriter. With the advent of word processors (and personal computers) people started using just one space after the period. I was totally unaware of this until a professional writer reviewed my resume. So here you are with your Twitter account all tweeted up, and your Facebook account with dates carefully hidden and a profile picture of you from 15 years ago, and only the last 15 years showing on your LinkedIn profile and you think you have hidden your age. If you are in the habit of putting two spaces after every sentence, you might consider removing that extra space from your resume. It is dating you.