I also have the habit of selecting a couple of lines to mark where I stopped reading before doing something else. Or even when I'm just scrolling down, to make

I also have the habit of selecting a couple of lines to mark where I stopped reading before doing something else. Or even when I'm just scrolling down, to make sure I don't scroll too much. But I don't seen anything wrong with reading online versus reading a long pdf document. As long as the text isn't split in a lot of small pages that take 15 seconds to load, it's ok.