One typo in a cover letter or resume can prove costly.
USA Today had an article posted yesterday morning Obama hails historic U.S.-Italian ties, friendship. I misread the headline as Obama halts historic U.S. –Italian ties, friendship. A couple of misplace letters changed the perception of the article entirely. The same holds true with your resume, cover letter, follow up communications during the job search and interview process. While the example is one of a mistake I made reading a headline, it could have just as easily been a typo in an email. This example makes the point it is extremely important you proof read any of your correspondence you send out. A spell checking or even a grammar checker would not have caught the mistake.