Press the 'tab' key to jump forward and 'shift' + 'tab' to jump backwards
<form>
<p>
<label for="firstname">First Name:</label>
<input type="text" name="firstname" id="firstname" tabindex="1" />
</p>
<p>
<label for="lastname">Last Name:</label>
<input type="text" name="lastname" id="lastname" tabindex="3" />
</p>
<p>
<label for="email">E-mail</label>
<input type="text" name="email" id="email" tabindex="4" />
</p>
<p>
<label for="address">Address</label>
<input type="text" name="address" id="address" tabindex="2" />
</p>
<p>
<input type="submit" name="submit" id="submit" value="Submit" tabindex="0" />
</p>
</form>