By Rachel Zupek, www.TheWorkBuzz.com, CareerBuilder's job seeker blog

Did you think I would say anything but "YES"? Of course mistakes on résumés and cover letters matter - isn't that what we've been telling you, and what you've heard for the past - forever?

If an employer is only looking over your résumé for about 30 seconds, you can bet that if what catches his eye in that time period is an error, your résumé is going in the trash. Same with your cover letter - why waste time reading something that you can barely understand?

Kate Lorenz, CareerBuilder.com Editor

In addition to reinforcing key skills and experience, a cover letter demonstrates your desire to work for the employer and the specific ways in which your expertise can benefit the firm. More importantly, it helps differentiate you from other job seekers and provides incentive to contact you for an interview.

Even if composition isn't your forte, you can still create a killer cover letter. Here's how:

By Robin Ryan, career expert and author of 'Winning Cover Letter'

The biggest mistake many job hunters make is skipping writing a cover letter when sending off a resume, says Jim, an AT&T human resource manager. He shares his insight, saying, "Cover letters are very influential, and a well written letter can grab an interview just on its own merit. It's too bad most job hunters are so lazy they don't write one. That's an error no savvy job hunter wants to make.

"Writing cover letters is hard for most people so they talk themselves into not doing it. That's number one on our "don't" list. We published a survey of over 600 hiring managers including the exact formula employers want you to use in "Winning Cover Letters."

Here are some key ones to keep in mind:

TORONTO (Reuters) - Typing mistakes in a job application can kill a would-be employee's chance of landing a job as employers bet that a sloppy resume means the applicant will do a sloppy job.

A telephone survey of 100 senior Canadian executives showed that more than a fifth of executives said a single typo on a resume or cover letter could cost a potential employee a job, while 28 percent said two mistakes would kill their chances.

The survey, published on Tuesday, was carried out by online job search firm Accountemps.

Selena Dehne, JIST Publishing

Most job seekers know that to land an interview they need more than a strong resume. They need a well-written cover letter to go with it. That doesn't stop them from trying to brainstorm any excuse they can to avoid having to write one.

Yet, skipping this critical step in the job search is one of the worst faux pas a job seeker can make.

"Job seekers should never send a resume to someone without explaining why," says Michael Farr, author of The Quick Resume & Cover Letter Book, Fourth Edition (JIST - 2008).

"Whether you're mailing, faxing or e-mailing your resume, it's important to provide a cover letter with it. Even when you post your resume to a job bank or employer Web site, the site often has a place where you can upload or paste a cover letter. The fact is most employers expect candidates to send both."

Writing a cover letter shouldn't be difficult or time consuming, even though many job seekers mistakenly believe it is. If a person has 15 minutes to spare, they have enough time to write a cover letter, according to Farr.