Hello!! can someone please explain to me the cause and effect of white supremacy?? thank you!!

The causes of white supremacy are rooted in slavery. Africans were perceived to be inferior to the white masters. Their native languages were not English, their skin was dark, their African customs were different, and they were to serve their owners/masters, who were of European ancestry and white. Read lots, it's a very complicated topic, with many manifestations:

http://www.bing.com/search?q=whit+supremacy&form=EDGNTC&qs=PF&cvid=9988a269e0bf44aabcb274c0dc3da1fa&pq=whit%20supremacy