Autism??????

What are the signs of Autism..can someone plz let me know? And what causes it?

Signs of autism almost always develop before a child is 3 years old, although the condition is sometimes not diagnosed until later.
Social interactions and relationships. Symptoms may include:
Significant problems developing nonverbal communication skills, such as eye-to-eye gazing, facial expressions, and body posture.
Failure to establish friendships with children the same age.
Lack of interest in sharing enjoyment, interests, or achievements with other people.
Lack of empathy. People with autism may have difficulty understanding another person's feelings, such as pain or sorrow.
Verbal and nonverbal communication. Symptoms may include:
Delay in, or lack of, learning to talk. Up to 50% of people with autism never speak.
Problems taking steps to start a conversation. Also, people with autism have difficulties continuing a conversation once it has begun.
Stereotyped and repetitive use of language. People with autism often repeat over and over a phrase they have heard previously (echolalia).
Difficulty understanding their listener's perspective. For example, a person with autism may not understand that someone is using humor. They may interpret the communication word for word and fail to catch the implied meaning.
Limited interests in activities or play. Symptoms may include:
An unusual focus on pieces. Younger children with autism often focus on parts of toys, such as the wheels on a car, rather than playing with the entire toy.
Preoccupation with certain topics. Older children and adults are often fascinated by train schedules, weather patterns, or license plates.
A need for sameness and routines. For example, a child with autism may always need to eat bread before salad and insist on driving the same route every day to school.
Stereotyped behaviors. These include body rocking and hand flapping.

Autism tends to run in families