I'm trying to design an email text editor that has a preview window next to it. Should the preview be on the right or left side of the editor? My reasoning is that the preview should be on the left side because majority of people are right-dominant so the immediate actions (editor) should be on the right, but I've seen editors with the preview on the left so which is more natural?
It partly depends on cultural norms. In the West, we're trained to read left to right, so I actually feel it makes more sense here to have the preview to the right of the editor.
For similar reasons (reading left to right), vertical navigation is usually to the left of the content it controls.