codice:
<?xml version="1.0" encoding="iso-8859-1"?>

  <!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" xml:lang="en" lang="en">
    <head>
      <title>Code Example by DYNAMIC+</title>

      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
      <meta http-equiv="Content-Language" content="en-us" />

      <script type="text/javascript">
      <!--

        function getNextItem( __objThis, __objItem, __cbMaxLength )
        {
          if ( __objThis.value.length >= __cbMaxLength )
            __objThis.form.elements[__objItem].focus( );
        }

      //-->
      </script>

    </head>
    <body>

      


        <form>
          <input type="text" name="primo" onkeyup="getNextItem( this, 'secondo', 6 );" />
          <input type="text" name="secondo" />
        </form>
      </p>

    </body>
  </html>