A tight labor market has kept employers on the Web, looking to fill jobs in their companies. Total online jobs ads grew to nearly 4.4 million in April, a 16 percent increase over last month, according to the Conference Board’s Help-Wanted Online Data Series. There were about three jobs advertised online for every 100 people in the workforce. Good news for workers: The most advertised jobs tended to be among the highest-paying —Â management and health care, which had a combined 850,900 vacancies nationwide.