Thank you. I spent some time experimenting with margin-left. It works very well for epub, but not in mobi. The Kindle only understands whole ems and text-indent, any margin-left or percentage changes give just one, fixed, space. text-indent also makes the space much bigger than you would expect. When I create more than 3 indents, if the enclosing div is styled, the forth and eighth lines sometimes, but not always, get converted to the em of the line above. I have not yet found out why.
The opposite is true for font-size in mobi. It does understand part ems but the difference is much smaller than you would expect.
Thank you also. I had not heard of PRSPlus. I will give it a try on my PRS-350 and also try embedding a font.