I would not reccomend these sties. Most of the universities or companies are aware of such sites that automatically generate cover letter so they will know right aware that you have not wirtten the letter nad you will be disqualified immediately. If you are trying to write a good resume then post it here in the forum tobe edited or contact any professional editing company such as
www.essayedge.com,
www.uni-essay.com or
www.accepted.com. They will help you for not that much money and eerything will be perfect.