Grammar mistakes aren’t just embarrassing—they can impact a company’s bottom line, too. When clothing retailer Old Navy released a line of college sports-themed t-shirts in 2011, they missed a small but very important piece of punctuation. Instead of writing “Let’s go, [team]!” they wrote “Lets go, [team]!” Old Navy received a large amount of flak from Internet commentators and news outlets alike. They eventually pulled the shirts and reprinted them with a corrected slogan. Let’s go, Team English!

This careless error cost Old Navy a lot of money, but even after they corrected the mistake, the evidence of it lives on through the magic of the Internet. Because information is archived indefinitely online—and because some sticklers love nothing better than pointing out grammar errors—even a minor goof can continue to haunt a company for years after the fact. When lingerie superstore Victoria’s Secret launched their new line—called simply “Body”—they struggled with punctuating it in their print and web ads. Although they eventually corrected the issue, their old ads featuring catchphrases like “You’ve never seen ‘Body’s’ like this!” and “See the ‘Body’s’ in action” will live on in snarky blog posts like this one.

Grammatical errors in product design, packaging, or marketing can materially damage a brand. According to Sean Coughlan, an education correspondent for the BBC, researchers estimate that spelling mistakes cost online retailers in the U.K. millions of lost sales each year. “Spelling is important to the credibility of a website,” Coughlan reported. “When there are underlying concerns about fraud and safety, then getting the basics right is essential.”

While high-profile errors like the ones mentioned above earn negative press, there are other ways that poor writing can undermine the credibility of a brand. We’ve become very adept, as a technologically advanced society, at tuning out what we don’t want to see and hear. An increasing number of companies use content marketing—value-rich blog posts, articles, and social media updates—to reach customers who are immune to traditional advertising. According to the Content Marketing Institute, the strategy is founded on “the belief that if we, as businesses, deliver consistent, ongoing valuable information to buyers, they ultimately reward us with their business and loyalty.”

With this new model of marketing comes an increasing pressure to deliver quality content that is both relevant and well-presented. Savvy companies know that it’s not just about churning out articles stuffed with keywords, but as marketers and entrepreneurs also understand, presentation is as important as content. A company whose online presence is marred by typos, sloppy writing, and substandard grammar is often perceived as sloppy and substandard in its products or services as well.

Most of these writing errors are the result of carelessness rather than ignorance. Grammarly, whose automated spelling and grammar checker catches these and many other mistakes, found that by sixth grade, most students have mastered the basics of written communication. Although students continue to obtain more sophisticated writing and reasoning skills, most online content is only at a basic (i.e. elementary school) or intermediate reading level according to Google. The search engine giant introduced a feature to filter search results by reading level, and a quick search for “news” shows that 43 percent of results are basic and 52 percent are intermediate, but only five percent are at an advanced level.

The statistics from Google show that companies don’t need to hire literature professors to write their blog posts or manage their Twitter feeds. However, attention to detail through careful proofreading—preferably by more than one set of eyes—can prevent costly grammar goofs.

The moral of the story: when you see a red line in your document, correct the mistake before it hurts your bottom line.