Tab order of close button in popup with tab panel

1. What determines the tab order?
2. What is tab order in accessibility?

What determines the tab order?

Control tab order is determined by the order in which controls are drawn on the screen. The first control that you draw is assigned a tab order of 1 , the next is given tab order number 2 , and so on.

What is tab order in accessibility?

The tab order should follow the visual flow of the page: left to right, top to bottom – header first, then main navigation, then page navigation (if present), and finally the footer.