Under federal law, the standard governing employer liability for a hostile work environment depends on whether the alleged harasser is a supervisor of the complaining employee or someone else, such as a co-worker, customer or other third party. If the alleged harasser is a supervisor, the employer will be strictly liable if unlawful harassment occurred and there was an adverse employment action. However, if the alleged harasser is a co-worker, for example, the employer can avoid liability if it promptly and reasonably …