Переход на след. input при заполнении поля
<script>
function testJump(x){
var ml = ~~x.getAttribute('maxlength');
if(ml && x.value.length >= ml){
do{
x = x.nextSibling;
}
while(x && !(/text/.test(x.type)));
if(x && /text/.test(x.type)){
x.focus();
}
}
}
</script>
<div>
<input type="text" onkeyup="testJump(this);" maxlength="5" size="5">
<input type="text" onkeyup="testJump(this);" maxlength="4" size="4">
<input type="text" onkeyup="testJump(this);" maxlength="7" size="7">
<input type="text" onkeyup="testJump(this);" maxlength="5" size="5">
</div>