This has been discussed before. The general opinion is the lower right. That comes from history - and the natural flow of the eye across and down the screen (for Western cultures). But consider these points.1. The main thing is that it is always in the same place on the screen. I once worked with some courses where it was there BUT the pages varied in height and width so the button was rarely in the same place on the screen. 2. Fixed screen size makes it very easy for the learner to know where everything is.3. On the other hand, if you could have some long pages (diagrams, report samples, etc.) then you might want to have a design that had and open ended bottom on the page with the nav in the upper right. I did a series of 40 courses and got NO complaints. The learner always knew where the next button was.4. Given 3, try not to put anything fixed on the bottom. Someday it will bite you. People are used to viewing web pages these days and vertical scrolling is not unusual.5. Horizontal scrolling is to be eliminated if at all possible. Nasty to have to scroll in both directions. Most mice have a roller that does the vertical scroll.6. Consider also offering key navigation such as allowing the user to use arrow keys or PgUp and PgDn to move around as well.
