It’s hard to believe that hiring managers and employers are surfing the Web to screen job candidates – or that anything your boss might dig up online might matter as much as your undergraduate major or references, but increasingly, it seems like it does.

A recent study conducted by Harris Interactive for CareerBuilder.com determined that 45 percent of employers questioned were using social networks to screen job candidates — more than double from a year earlier, when a similar survey found that just 22 percent of supervisors were researching potential hires on social networking sites like Facebook, MySpace, Twitter and LinkedIn.

One easy thing you can do to gauge of how much digital dirt there is muddying up your online reputation is by Googling yourself, said Peter Spicer, a personal risk specialist . If, for example, you have your annual beer pong tournaments memorialized on Facebook and MySpace, you might want to consider deleting those pictures or at least untagging yourself in them or ensuring that your privacy settings are set so that people outside of your network can’t view them. Choosing a slightly more respectable profile photograph of yourself couldn’t hurt, either.

“First impressions are crucial to landing a job, particularly in the current job market,” said Mr. Spicer. “A job candidate with no embarrassing photos online has an immediate edge over you if there are pictures of you on Facebook wearing a lampshade and holding a martini.”

If you cringe at what surfaces after a cursory Google search — like photos from that hotdog-eating contest you won in 1995 — you could always try creating your own content online, like a LinkedIn account or Google profile, to help buffer it out, but “a better idea is to think twice before posting any public content you wouldn’t want found by potential employers,” said David Binkowski, senior vice president of marketing at MS&L, a communications firm.