Very interesting! I also noticed before with percentage (NN/Moz) that if you resize the browser width (dramatically - like 50%), the indent class starts to 'kick-in', but at different amounts. From what I understand, the percentage should be based on the containing block (the <div> above?), so I really couldn't figure out why the lines weren't calculating that width the same.
Also read an old blerb in a css text about Netscape having trouble with padding as % when using it with float, but it seemed outdated. I couldn't find anything on Netscape's site and didn't test it for myself. Anyway, the page looks great now!