UX design focuses on the user flow and how easy it is for the user to accomplish a desired goal. For this reason, whenever I create a UI, I take into account three things: heuristic thinking, choice modelling and compromise effect.
Let’s take the Gmail and Amazon sign-in pages as an example to show you how these concepts might apply to real-life. The tab order is important when you navigate a form with the keyboard. Users should be able to tab through the elements in a logical order. Below we have two different sign-in pages and user experiences:
Amazon implements the UI correctly by following these three principles:
Allow users to solve problems and make judgments quickly.
Assign a value to each form element based on probability (logical order).
Avoid users selecting an extreme choice. In this case “Forgot email?”.
It’s worth mentioning that using tabindex values greater than zero to control the tab order is considered a bad idea. The tabindex attribute is often set by developers who don’t have any idea of what the user expects. The tab order should follow a pattern that is logical from the user’s perspective.