For example, when you move from a printed page to a computer screen. you swap a simple rectangle for a crowded display and have to deal with the fact that monitors vary a great deal in size and shape.
A common solution is to have sections of the page that vary in width and produce scroll bars as you move around.
That's great for things like news sites where cramming in a lot of information is important.
But on our Green Orange site, for example, we have gone for attractive square pages - and to make sure that they look good on a small screen, have opted for a lot of smaller pages instead of fewer larger ones.
Your site might need something different again - and we'll discuss what's best for you before we start work.