If you open any file, you can browse through using buttons ← a → in the toolbar or you can use menu items in File menu popup (next file and previous file). File listing is sorted using criteria selected in settings dialog. If you have opened multimedia or image file, you can use also keys space and F11 (next) and backspace and F10 (previous) (note: you can use F10 and F11 by any file). If you selected to view text or binary files too, it's possible, that you encounter some file of this type - you will not be able to use space and backspace buttons in this case (because they are used for file editing :-) and you should use F10, F11, toolbar buttons or menu items...