Mercury not travelling in a straight line?

[seb7]

Take a look at this..

http://sunearth.gsfc.nasa.gov/sunearthday/media_viewer/flash.html
Navigate > Visualizations > Mercury Transit of the Sun

Why is Mercury travelling up and down vertically?

I can understand on most given view points it would not be a straight line, but the line of movement in the video is just weird.

[russ_watters]

I'm not seeing what you are seeing. I see it being a little jerky due to an inconsistent framerate, plus the "camera" pans right in steps, but I don't see much if any up and down motion.