An ugly insight into the mind of hiring managers: they’re looking for reasons to reject applicants. A manager’s day can disappear quickly if a company is actively hiring so they have to be brutal when reviewing applications and typos are easy to spot and condemn. Did you catch the typo in the headline? How did you feel? Don't let anyone feel that way about you.
We all make mistakes when emailing friends or posting Tweets but if you’re serious about a job you need to proof your cover letter, resume and emails. If you can't focus, have a friend proof your material. Mistakes communicate volumes about your attention to detail. If you’re freakishly talented a typo may not work against you but a hiring manager may not get to your portfolio if your resume has mistakes.
Don't be laughed at or discarded. Destroy all typos.