Almost everyone holds prejudices that they are not even aware of. Harvard has created tests that measure prejudice through quick presentation of certain factors, so you can see what prejudices you hold that you may not be consciously aware of. For instance, when stimulus are presented in a rapid manner in which you cannot consciously perceive, most white participants will react more negatively to black race - an example that has been called modern racism.
See what prejudices you hold: https://implicit.harvard.edu/implicit/
(I took the race and sexual orientation tests. Take with an open mind, because most of these prejudices are held societally and are not an indication of your character.)