Use the "TabIndex" attribute:
<input type="text" name="three">
<input type="text" name="two" tabindex="2">
<input type="text" name="one" tabindex="1">
<input type="text" name="four" tabindex="0">
The tab order above is one, two, three, four because the positive TabIndex values receive focus first.
TabIndex = 0 or no TabIndex are visited after the elements with a positive TabIndex and receive focus based on which appears first.