Legacy app users know the data imput screens they use inside and out, sometime never having to look up when entering data because they know the forms that well. We need to mimic this when we move these legacy apps to the web and one way to help us using the tabindex element.
Tabindex allows you to set the tab order of inputs, select lists, form elements and even buttons. In APEX we can do this by filling in the HTML Form Element Attributes input on our item edit screens. Set your tab order by simple adding "tabindex=x", with x being a number. Want to skip an element? Set the tabindex to be -1.