The line you see is probably actually blank space surrounding the sprite.
Look at the sprite in zoom and if it does not fill the sprite box that is your problem.
The way to solve it is to select and cut the sprite and set the sprite box to a smaller dimension and then paste the sprite back and select expand sprite box to fit.
That will remove the blank spaces so tiles align with no lines.
its not sprite, its a tiled background. and my background is fine. and i seen this problem posted here before, but no solutions. when i turn off webGL the black line become a bit transparent . but it still exists