White line/spots?

Hello, I have a macbook 7,1 and am still under waranty by about a month. Lately, there seems to have appeared a white line followed by a spot in the center of my screen. At first I thought it was just dirty and cleaned my screen, but it didn't go away. I've had this line for a while and it is very annoying when watching movies on my macbook. My question is, what are these lines? Is this problem common? Are they dead pixels? Can they be fixed? Is it covered by the Mac warranty and can I go to an apple store and have it fixed? Any help is appreciated. Thanks in advance.