When filling out your contact form you may find that the tab button doesn't go to the next box and instead skips around and goes out of order. This is due to the arrangement of elements in the left side Site Panel of the Design App. To set your form up to tab from field to field, order the elements for the input boxes in order from first to last in the left panel.
The first input box should be above all other input boxes for the contact form, with the next input box underneath that one.