This is a Tiled Background.
<img src="http://dzner.pro.br/land.png" border="0" />
Whenever I do a Tiled Background, this line comes next. How can I fix it?
It's probably a single pixel lining the edge of the image itself.
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.
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And there's no way to avoid this?
Well, ideally you would use sprite objects for terrain tiles. This tutorial by Ashley explains it really well. scirra.com/tutorials/253/how-to-make-a-platform-game
Hope that helps.