def replace_line(old_line, new_line, lines):
    """
    Replace single line in the html file

    :param old_line:    the line to be replaced
    :param new_line:    the line that will replace old_line
    :param lines:       current contents of html file
    :return:            new contents of html file
    """

    edit_index = lines.index(old_line)
    lines[edit_index] = new_line

    return lines