Setting the tab order is a Design mode activity that determines the order in which controls get focus (become active) for user input in Run mode in response to the TAB key being pressed.
In Run mode, the tab order is relevant only to controls that can accept input focus, ie edit boxes, combo boxes, radio buttons, etc. Graphic controls such as lines, rectangles, circles and polylines do not feature in the tab order.
You can also enable or disable the tab order properties of controls through their Tabstop property in the Property Sheet. The control will not become active if you set its Tabstop property to 0 - False in the Property Sheet, irrespective of where it appears in the Tab Order list
Note: In Design mode all controls are shown in the tab order.
Controls that can not accept input focus are shown in blue in the Tab Order window.