Generally, employers can monitor any company-owned computer or phone. And they can act on what they find. Evidence that you are violating company policies -- using devices for personal communications, for example, online shopping or any one of dozens of perfectly legal activities that happen to be barred by your employer -- can cost you your job. And illegal activities -- gambling or dealing in pornography, for example -- are a no-brainer.

There's plenty of software available that makes it easy for employers to monitor Internet use, e-mails, software downloads, what websites you visit and how long you stay, instant messaging and chatting, etc. In fact, at least two-thirds of employers already monitor Web usage, and the share is likely to increase. There are some restrictions on employers' monitoring, however. For example, union contracts sometimes contain provisions limiting the monitoring of workers' computer activity.

The law forbids employers from discriminating in any aspect of employment -- hiring, firing, pay, job assignments, promotions, layoffs, training, fringe benefits and so on -- because of pregnancy. But if you work for a private firm with fewer than 15 employees, you may be out of luck -- these are exempted.

If pregnancy prevents you from performing your job, your employer must treat you the same as any other temporarily disabled worker -- providing light duty or alternative assignments, for example. And your boss has to hold your job open for a pregnancy-related absence for the same amount of time jobs are normally held for workers on sick or disability leave.

Though 21 states and the District of Columbia bar workplace discrimination on the basis of sexual orientation, there is no such federal prohibition on the books, so gay workers in 29 states can legally lose their jobs. Legislation is pending in Congress that would ban discrimination in hiring, firing, promotions, compensation and other employment practices because of a person's sexual orientation. The law would apply to employers with 15 or more employees. But the prospects for passage are iffy.

The 21 states where workplace discrimination based on sexual preference is barred are California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Iowa, Maine, Maryland, Massachusetts, Minnesota, Nevada, New Hampshire, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Washington and Wisconsin.

You can't lose your regular job if Uncle Sam calls. Federal law stipulates that employers must reinstate reservists and National Guardsmen to their former jobs or comparable positions after active duty.

There are some conditions, however, to be eligible for reinstatement: Service members must give advance notice prior to leaving; be on active duty for less than five years; not be dishonorably discharged; and report back to work in a timely manner after discharge. What's more, if you can no longer perform your old job, your employer must use reasonable efforts, such as training, to enable you to upgrade or refresh your skills to become qualified for the position. And the company can't consider time on active duty a break in employment for purposes of pension benefits and vesting. As far as they go, the time spent on active military service is the same as time spent with the company.

Whether your tat is a tasteful rosebud on your ankle or a screaming skull on your forearm, your employer can insist that it be hidden. The no-visible-tat policy must, however, be imposed across the board and not just on some workers. Many employers simply ask workers to use their own discretion in deciding whether to cover body art, which is becoming increasingly common, especially with younger employees. About 38% of the millennium generation -- ages 18 to 29 -- sport at least one tattoo (compared with just 15% of baby boomers). 18% of millennials have six or more.

Most private employers can't use lie detectors for preemployment screening or during employment. The exceptions: Federal contractors doing national security or intelligence work, drug manufacturing and distributing firms, and some security services, such as armored car, alarm and guard services. There's also a limited exception for a firm undergoing an investigation into theft, embezzlement, industrial espionage and so on. Government employees can be compelled to take a polygraph.

Even when a lie detector test is OK, an employee has certain rights. You can refuse to take the test or stop it at any time. You can't be fired or demoted for doing so, nor can you be demoted or fired based solely on the test results. When a polygraph is allowed because of ongoing investigations, a written or verbal statement must be provided prior to testing, outlining what is under investigation and the basis for the employer's suspicions.

If "English-only" is needed to ensure the safe or efficient operation of the business, an employer can set rules. In a work situation where clear communication between all present could be critical -- in a hospital operating room or laboratory where toxic chemicals are used, for example -- insisting on speaking in a foreign language can get you disciplined.

But the policy can't be put in place for discriminatory reasons, and any English-only policy, even if it is justified, must be applied evenly. The Equal Employment Opportunity Commission recently settled a case, awarding nearly $1 million to Filipina nurses who were disciplined for speaking their native Tagalog on the job, while Spanish-speaking colleagues were not.

Federal law requires employers to make reasonable adjustments to work conditions and schedules to let workers practice their religions. In most cases, your boss would have to allow you to use regular time off to observe Ramadan -- or Yom Kippur or Christmas. Similarly, dress or grooming practices for religious reasons must be accommodated. Sikhs are allowed uncut hair and beards; Orthodox Jews, their yarmulkes; Muslim women, their head scarves; and Rastafarians, dreadlocks, for example.

But there is a loophole that gives some employers an out: If reasonable accommodations would cause more than a minimal burden on the operations of the business, an exemption is made. Some examples: Fire and police departments, if there aren't enough personnel to accommodate all requests for time off and maintain adequate staff for emergencies. Or a Jewish deli where all employees want the Sabbath off, leaving no one to make the brisket.

If you work for a business with more than 50 employees (or any part of government), you can take up to 12 workweeks of unpaid leave over a 12-month period if you or an immediate family member has a serious illness. During that period, your job is protected. To be eligible, however, you must have been on the payroll for a total of 12 months and worked at least 1,250 hours over the previous 12 months (an average of 25 hours a week).

Sometimes an employee can take Family and Medical Leave Act leave intermittently, in separate blocks of time for a single qualifying reason, or regularly work a reduced schedule. When leave is needed for planned medical treatment, the employee must make a reasonable effort to schedule treatment so as not to unduly disrupt the employer's operation.

There is no federal law requiring employers to give workers meal or rest breaks. Only 22 states plus Puerto Rico and Guam have statutes specifying meal breaks, and in some of them, the law applies only to certain types of workers -- hotel room cleaners, in Illinois, for example. Pennsylvania law deals only with seasonal farmworkers. In New Hampshire, workers can be told to keep working while eating -- if that's feasible.

Federal law does make it clear that if a meal break is provided, workers are off the clock -- as long as the break is at least 20 minutes and the employee is relieved of all work during the time. By the way, most workers do have a federal right to bathroom breaks.

However, he or she can make it awfully difficult to smoke. Any employer can impose restrictions on when and where employees can light up in the workplace. Your boss can also legally discount health insurance premiums charged for your nonsmoking colleagues, effectively raising premiums for those who continue to puff away. Often you can avoid the higher premium by participating in a smoking cessation class.

An employer also can't force an employee to lose weight, though an overweight worker can be fired if the excess pounds prevent performance of the essential functions of the job. A flight attendant who can't navigate the narrow aisles of an aircraft, for example, can be let go. But employers need to tread very carefully, lest they run afoul of the Americans with Disabilities Act, which protects individuals unable to perform a "major life activity." They must be provided reasonable accommodation if that will allow them to perform the job. An employer might, for example, have to provide a morbidly obese employee with a golf cart to get around a factory.

There's no law protecting you if you bad-mouth the company that issues your paycheck. Recently the National Labor Relations Board, the federal agency that enforces federal labor law, issued its first decision on employee expression on social media. It upheld the firing of a salesman who dissed his employer on Facebook.

There are some free speech protections, however: The National Labor Relations Act protects group actions of workers who use social media or other outlets to discuss improving the terms and conditions of their employment -- pay and safety, for example. So comments on social media are safeguarded if they are undertaken on behalf of a group. But workplace laws haven't kept up with the advance of technology and the advent of social media, so there's a lot of gray area here, and a lot of cases are likely to wind up in the courts.