Selena thinks that all computer programmers are antisocial and boring. Even before meeting Mark, a computer programmer, Selena decides that she will not like him. Selena’s beliefs are , and not liking Mark is .

stereotype/prejudice

Explanation:

Selena is acted in a biased manner since she has preconceived notions of computer programmers and when meeting Mark, she is projecting these beliefs rather than being open to observe Mark and find out something different:

The act of deciding ahead is a prejudice that can harm social relationships.

Generally speaking, prejudices result from bad stereotypes and affect the people chances to develop potential and have better relationships and they also damage the self-esteem and mental well being of individuals.