Side Look neat Content Parts are easy to update without redoing all pages.
New pages can be just the content part while the navigation portion remains in place.
This means less maintenance for navigation sections. Multiple-column text can't be read by screen readers. For large areas of text, need to use one column. If so, the SSI's would not be available unless the users also had server software working on their home machines. Users who are taking the course because they travel may already have to pay a higher price for ISP's with national or international dial-up numbers.