No matter how much you "like" Facebook, browsing the tremendously popular social website at work could actually be against federal law, according to Business Insider.
Whether navigating to Facebook — or other places like Amazon — is legal or illegal depends on interpretation of the Computer Fraud and Abuse Act of 1986.2 comments on this story
"For the past decade or so, courts have disagreed over the scope of the Computer Fraud and Abuse Act," Stephanie Green and Christine Neylon O'Brien, two professors at Boston College, wrote in a paper that discussed the issue. "Some courts have found that an employee who violates a workplace policy, breaches a contract, or breaches a duty of loyalty to his employer may be both civilly and criminally liable under this Act."
Through the law, it is illegal to knowingly exceed any authorized use of a computer. If a company doesn't specifically allow a site, such as Facebook or Amazon, it's been ruled illegal to visit it.
There is uncertainty in this though. Recently in United States v. Nosal it was ruled that it wasn't a violation of the act to avoid corporate computer access policies, but this decision went against past rulings by other appeals courts.