You've got spelling and grammar checkers on your laptop computer, so you're all set to crank out the perfect sales letter while you're on the road.

But Chandra Clarke and Terence Johnson of the online editing service Scribendi.com would urge you to not hit the "print" button just yet. Those spelling and grammar checkers can make mistakes, and even one typo could not only ruin the impact of your letter but reflect poorly on you and your company.

Written marketing materials are often the first impression prospective customers have of a company. And prospects can be very unforgiving of those little typos.

In the article "Ethos and Error: How Business People React to Errors," University of South Alabama English professor Larry Beason found that mistakes in written materials create confusion regarding meaning and harm the image of the writer and the writer's company. The typos often reflect on more than the writer's communication skills, Beason said. The people he interviewed called sloppy writers "hasty," "uninformed," "careless" and "uncaring."

"If you don't care about your work," wrote one of the respondents, "why should I care about you and your business?"

But carefully proofreading your work may not be enough - studies show that people often miss their own typos. According to the studies, you see what you expect to see in your own writing, rather than what's actually there. Another person, or an editing service like Scribendi, can provide a fresh set of eyes.

Scribendi offers a variety of services, including proofreading, editing and translation. Clients upload their files to Scribendi's Web site and download their documents after the editors are done correcting and polishing.

The editors come from a variety of backgrounds, so they're familiar with their clients' fields. In addition to correcting grammar, spelling, flow and consistency, they explain word usage issues and standard writing practices, so clients learn how to improve their own writing.

When it comes to making a great first impression, Clarke and Johnson believe no project is too small. The image you create with a short press release, they say, is as important as a deal-closing presentation.