It looks like you're trying to use the tiled background for your terrain tiles. What the tiled background is for is like sky textures or any other images that can repeat infinitely in a direction without seams between them. Unless I'm mistaken, that line is the right edge of your image starting to repeat again.
Well, ideally you would use sprite objects for terrain tiles. This tutorial by Ashley explains it really well. http://www.scirra.com/tutorials/253/how-to-make-a-platform-game Hope that helps.Ahr Ech2013-02-02 21:41:01