The following is written in the Old Testament of the Bible:
"A woman must not wear men's clothing, nor a man wear women's clothing, for the Lord your God detests anyone who does this."1
The purpose of this prohibition was to maintain the distinction of the sexes. A woman was not to dress as a man would, and a man was not to dress as a woman would with the intention of deceiving others into believing they were of the opposite sex. We, also, see this biblical principle carried over in the New Testament of the Bible.2
In answering your question, a man is not to wear his hair in an effeminate manner (as a woman would.) This does not prohibit a man from having long hair, however, as long as his hair is worn in a manly manner and not as a woman would wear her hair.
2 (1 Corinthians