i think it is necessary to indicate at least range of salary. of course the candidate is wondering about the wage.. if she is already working she wants to know if it's worth it to take a day off to attend the interview, or not to bother in case the offered salary is the same or lower. Actually I think the employer must post the salary to avoid misunderstanding and wasting of his time and time of the candidate. I would be quite angry if I had to waste few hours (probably to escape from work) just to find out that I am offered half of my present salary.