I cant close safari after using it. Have to unplug computer to get rid of it.

Try opening the Activity Monitor, choosing Safari, and hitting the x in the top left corner to force quit it.

You can find Activity Monitor by using spotlight search (the magnifying glass in the corner), and typing Activity Monitor.

Have you tried to force quit it?

You can do this by going to Apple Menu > Force Quit, and selecting Safari from the list.