Cancel | OK

There's a big debate of what the ordering of two-button dialogues should be. Should "Cancel" appear on the left or right of "OK" ("Cancel | OK" or "OK | Cancel"). There are certainly arguments for both sides.

The argument for "OK | Cancel" is that, at least for those who read left to right, is that you will see the action you most likely want ("OK") and will press it. This argument says you don't need to read cancel because you've already decided on what to press. There are several things wrong with this. Designing for the use case that users will not and should not read the second button (often a word or two) is an awful idea. The only people that should be able to navigate effectively through an interface without reading the second option are users that are extremely familiar with the interface and know all of the interface's dialogues. If a "pro" user already knows the interface well, the meaning of buttons being on the left or right is almost meaningless. The pro user will immediately move their cursor, stylus, or finger to the button and activate the correct button. Now, less talk about the new user that is not familiar with the dialogue box. I think it's safe to assume that the user will read all options before choosing one. If they read all the options, the more likely option will result in having to read the affirmative action, then the negative action, only to go back to the left and read the affirmative action again. This makes the user have to move their eyes in three places (after first reading the dialogue's title and body text) and move their eyes in two directions (first to the right, then back to the left).

Now, so far we've only talked about positioning based on how fast the user will be able to glance at the dialogue and decide what to press. What about which decision makes more logical sense? Again, the answer is also negative on the left and affirmative on the right. All of these are assuming the native language is read left to right and all these answers should be flipped with languages read right to left. If one reads in one direction, that direction should be representative of moving forward, and the opposite side is representative of moving backwards. Affirmative actions are typically seen as moving forward, and negative actions are moving backwards. Let's look at a dialogue book like a page in a book. If there were two buttons at the bottom of the page that would either bring the user back (re-read) or to the next page (continue), the user would certainly expect the button on the right would bring them to the right and continue reading, where the left button should bring them back.

In summary, buttons with negative actions on the left and buttons with affirmative actions on the right.

Finally, a related argument is the naming of the buttons. The buttons should always always always be labelled with the actual action they perform and not a generic yes/no answer that is dependent on the text above it. Answers like yes/no are very often unclear and can frustrate users when deciding which one is correct and can create undesired outcomes. A very common dialogue, the save dialogue, should have buttons labelled as "Don't Save" ("Cancel" can work in some contexts) and "Save". Not only does this make it more clear on what each button does, but it also makes it great for those pro users who love to skip reading the body of the dialogue box.