Using a Logical Keyboard Navigation Order
A logical keyboard navigation order should be used to ensure that dialog boxes and similar groups of objects can be traversed in a logical order using the keyboard, normally from right to left and top to bottom. If the order does not follow this convention, it can be very confusing to users who navigate using the keyboard. It is especially confusing for people who are blind and rely on screen review utilities. Users who are blind explore a dialog box sequentially, instead of scanning the entire box as sighted users would, so random tab order can make the dialog box nearly unusable.