For example, people love putting up photos of the wild time they had on Friday night or they'll put up photos of themselves doing questionable things.
Of course, not all users go on Facebook and Twitter to post potentially damaging images of themselves, but clearly the ones who do might want to be a little more cautious.
There have been reports in the last year about how employers are checking Facebook more and more these days to weed out possible candidates.
Online behavior study
But a new study conducted by North Carolina State University finds that a lot of employers and companies don't really understand online behavior and many Facebook users aren't getting hired as a result.
In the study, 175 participants were examined individually so researchers could measure their personality traits. The traits that were documented were things like conscientiousness, agreeableness and extraversion, which researchers said a lot of employers are seeking.
Afterwards, participants were tested on their Facebook use, which researchers compared to certain personality traits.
"Companies often scan a job applicant's Facebook profile to see whether there is evidence of drug or alcohol use, believing that such behavior means the applicant is not conscientious, or responsible and self-disciplined," said Dr. Lori Foster Thompson, professor of psychology at NC State and co-author of the study.
Misunderstood?
Meaning, just because you post a photo of yourself drinking beers with your buddies, it doesn't mean you're a drunk. And it certainly doesn't mean that you won't be a good employee. But that's not how many employers see it, researchers say.
"This means companies are eliminating some conscientious job applicants based on erroneous assumptions regarding what social media behavior tells us about the applicants," said lead study author Will Stoughton.
In addition, Stoughton said employers will need to look at what's being said on Facebook instead of just looking at the photos, since posted messages provide a better clue on what a candidate might be like.
"If employers plan to keep using social media to screen job applicants, this study indicates they may want to focus on eliminating candidates who badmouth others, not necessarily those who post about drinking beer," said Stoughton.
More discriminating
And that percentage is nine points higher than last year's study.
Additionally, researchers found that 39% of companies now use sites like Facebook and Twitter to look for future employees, which is also slightly higher than last year.
Disqualifiers
What were some of the things on social media pages that made employers not want to hire someone?
About 50% of employers said candidates posted photos or information that was either inappropriate or provocative, and 48% saw a candidate using drugs or alcohol on their page.
In addition, 33% of employers noticed a candidate that bad-mouthed a current or former employer, 30% noticed bad communication skills on the candidate's page and 28% noticed that a candidate made horrible remarks about a person's race, religion or gender.
And a good number of employers (24%) noticed candidates who lied about their qualifications, and they found this out by what candidates posted on Facebook.
On the plus side
When it came to the social media posts that made employers want to hire someone, 57% said it was because a candidate displayed a professional image on their social media page.
Moreover, 50% of employers felt a candidate had a good personality because of what he posted on social media and 50% liked a candidate because his social media page made him seem well-rounded.
Rosemary Haefner, vice president of CareerBuilder's human resources department, says people should manage their social media page in a way that makes them look good to the professional world, not just good to their friends and family members.
"Employers are using all the tools available to them to assure they make the correct hiring decision, and the use of social media continues to grow," she says. "For job seekers it is essential to be aware of what information they're making available to employers, and to manager their online image. At the same time, hiring managers and human resources departments must carefully consider how to use information obtained from social media and whether it is relevant to a candidate's qualifications."