HTML and CSS are very, very explicitly not WYSIWYG. Their specifications are crystal clear on this point. The same HTML document can and should be displayed dif

HTML and CSS are very, very explicitly not WYSIWYG. Their specifications are crystal clear on this point. The same HTML document can and should be displayed differently depending on device. Your ebooks are also not WYSIWYG. They're also specifically designed to display differently on different devices, and according to user preferences for things like font, text size, brightness, background, line spacing, etc.. WYSIWYG is exactly the opposite of these formats, and does not depend on the device. Postscript and PDF are WYSIWYG.