samsung 50 inch full HD plasma tv almost invisible lines, plus mirroring?

[Sawyer]

I have a samsung 50 inch full hd plasma tv for over a year now and I love it, picture quality is great, great for gaming.. but ever since I bought it I noticed there were two almost invisible horizontal parallel lines above the middle of the screen, you can only see them if you concentrate on them and look closely and if the background is of a light or bright color.. theres another problem.. when theres a dark object on a light background.. like black letters on a white background.. you can see.. also just barely though... that the letters or dark object is being mirrored horizontaly on boths sides till the end of the screen.. now I went back to the store when I bought it and there the same model tvs had the same issues so I dont think anything is broken... and it didnt get worse after a year.. but my question is.. what are the lines and the mirroring there? is it normal? and can it get worse over the years? thanks