Hmm, I have no trouble seing it. Try going here: http://www.allopticalillusions.com/optical...?sort=date&dir=

I created an image in paint to point something out. The pieces on the left are from the first triangle and on the right is the corrsponding place in in the second triangle. If you look closely you can see that the line is slightly different in the second triangle, this must means that the hypotemuse bulges out a little.

I don't think that would be very significant.

But it's there and and it seems suspicious, it might not be that on it's own but something is making the hypotemuse bulge in the second triangle.

I don't think its anything, looking back it seems the line on the bottom triangle is drawn thicker.