1) pdfs in portrait instead of landscape. Since most screens will display a complete page in landscape, why do the morons make pdfs in portrait, so you have to scroll and scroll, or even worse, two column portrait so you have to scroll from the end of column 1 at the bottom of the page to the start of col2 at the top of the page ?
2) multiple clicks - don't get me started on this one, two or even three clicks to get to a pdf
3) white text on black background, or green text on blue, or whatever. For 3 thousand years, the std has been black text on white background. IF something persists for 3,000 years there is probably a reason.
4) Typos - quite common on the english language sites of japanese firms, I guess they consider Americans not worth the effort, but surprisingly common on american and european sites as well.