Hola
mexbale
Lo único que te falta es crear el form:
Aquí lo puedes ver (testado en ie8, chrome5 y opera10)
Código HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Tabulación automática</title>
<script type="text/javascript">
function tabular(evt, obj, tam) {
tecla=(document.all) ? evt.keyCode : evt.which;
if(tecla==8) return; // para la tecla de retroceso
var frm=obj.form;
var largo = obj.value.length;
if (largo == tam) {
for(i=0;i<frm.elements.length;i++)
if(frm.elements[i]==obj) {
if (i==frm.elements.length-1) i=-1;
break }
frm.elements[i+1].focus();
return false;
}
}
</script>
</head>
<body>
<form id="frm">
<table width="950" align="center">
<tr>
<td colspan="2" style="border-bottom:1px dashed #A60C00"><strong>1. IDENTIFICACION GEOGRAFICA</strong></td>
</tr>
<tr>
<td style="border-bottom:1px dashed #A60C00"><div align="right">ENTIDAD FEDERATIVA</div></td>
<td style="border-bottom:1px dashed #A60C00"><div align="right">
<input name="CVE_ENT" type="text" id="CVE_ENT" size="2" maxlength="2" onkeypress="return tabular(event, this, this.maxLength)" /></div>
</td>
</tr>
<tr>
<td style="border-bottom:1px dashed #A60C00"><div align="right">MUNICIPIO O DELEGACION</div></td>
<td style="border-bottom:1px dashed #A60C00"><div align="right">
<input name="CVE_MUN" type="text" id="CVE_MUN" size="3" maxlength="3" onkeypress="return tabular(event, this, this.maxLength)" /></div>
</td>
</tr>
<tr>
<td style="border-bottom:1px dashed #A60C00"><div align="right">LOCALIDAD</div></td>
<td style="border-bottom:1px dashed #A60C00"><div align="right">
<input name="CVE_LOC" type="text" id="CVE_LOC" size="4" maxlength="4" onkeypress="return tabular(event, this, this.maxLength)" /></div>
</td>
</tr>
<tr>
<td style="border-bottom:1px dashed #A60C00"><div align="right">CLAVE DE AGEB</div></td>
<td style="border-bottom:1px dashed #A60C00"><div align="right">
<input name="CVE_AGEB" type="text" id="CVE_AGEB" size="4" maxlength="4" onkeypress="return tabular(event, this, this.maxLength)" /></div>
</td>
</tr>
<tr>
<td style="border-bottom:1px dashed #A60C00"><div align="right">MANZANA</div></td>
<td style="border-bottom:1px dashed #A60C00"><div align="right">
<input name="MZA" type="text" id="MZA" size="3" maxlength="3" onkeypress="return tabular(event, this, this.maxLength)" /></div>
</td>
</tr>
</table>
</form>
</body>
</html> Saludos