function checkEmail (emailStr) {
/* The following pattern is used to check if the entered e-mail address
   fits the user@domain format.  It also is used to separate the username
   from the domain. */
var emailPat=/^(.+)@(.+)$/
/* The following string represents the pattern for matching all special
   characters.  We don't want to allow special characters in the address.
   These characters include ( ) < > @ , ; : \ " . [ ]    */
var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"
/* The following string represents the range of characters allowed in a
   username or domainname.  It really states which chars aren't allowed. */
var validChars="\[^\\s" + specialChars + "\]"
/* The following pattern applies if the "user" is a quoted string (in
   which case, there are no rules about which characters are allowed
   and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
   is a legal e-mail address. */
var quotedUser="(\"[^\"]*\")"
/* The following pattern applies for domains that are IP addresses,
   rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
   e-mail address. NOTE: The square brackets are required. */
var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/
/* The following string represents an atom (basically a series of
   non-special characters.) */
var atom=validChars + '+'
/* The following string represents one word in the typical username.
   For example, in john.doe@somewhere.com, john and doe are words.
   Basically, a word is either an atom or quoted string. */
var word="(" + atom + "|" + quotedUser + ")"
// The following pattern describes the structure of the user
var userPat=new RegExp("^" + word + "(\\." + word + ")*$")
/* The following pattern describes the structure of a normal symbolic
   domain, as opposed to ipDomainPat, shown above. */
var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")


/* Finally, let's start trying to figure out if the supplied address is
   valid. */

/* Begin with the coarse pattern to simply break up user@domain into
   different pieces that are easy to analyze. */
var matchArray=emailStr.match(emailPat)
if (matchArray==null) {
  /* Too many/few @'s or something; basically, this address doesn't
     even fit the general mould of a valid e-mail address. */
    return false
}
var user=matchArray[1]
var domain=matchArray[2]

// See if "user" is valid
if (user.match(userPat)==null) {
    // user is not valid
    return false
}

/* if the e-mail address is at an IP address (as opposed to a symbolic
   host name) make sure the IP address is valid. */
var IPArray=domain.match(ipDomainPat)
if (IPArray!=null) {
    // this is an IP address
      for (var i=1;i<=4;i++) {
        if (IPArray[i]>255) {
            return false
        }
    }
    return true
}

// Domain is symbolic name
var domainArray=domain.match(domainPat)
if (domainArray==null) {
    return false
}

/* domain name seems valid, but now make sure that it ends in a
   three-letter word (like com, edu, gov) or a two-letter word,
   representing country (uk, nl), and that there's a hostname preceding
   the domain or country. */

/* Now we need to break up the domain to get a count of how many atoms
   it consists of. */
var atomPat=new RegExp(atom,"g")
var domArr=domain.match(atomPat)
var len=domArr.length
if (domArr[domArr.length-1].length<2 ||
    domArr[domArr.length-1].length>3) {
   // the address must end in a two letter or three letter word.
  return false
}

// Make sure there's a host name preceding the domain.
if (len<2) {
   var errStr="Esta direccion es desconocida como IP!";
   return false;
}

// If we've gotten this far, everything's valid!
return  true;
}


function validaFecha(Cadena)
{
    Fecha= new String(Cadena);  // Crea un string
    var patron = /^(0[1-9]|1\d|2\d|3[0-1])\/(0[1-9]|1[0-2])\/\d{4}$/;
    if (!patron.test(Fecha)) return false;
    // Cadena Año
    var Ano= new String(Fecha.substring(Fecha.lastIndexOf("/")+1,Fecha.length));
    // Cadena Mes
    var Mes= new String(Fecha.substring(Fecha.indexOf("/")+1,Fecha.lastIndexOf("/")));
    // Cadena Día
    var Dia= new String(Fecha.substring(0,Fecha.indexOf("/")));

    var Bisiesto = Ano%4 == 0 || (Ano % 400 == 0 && Ano % 100 == 0);
    // Valido el año
    if (isNaN(Ano) || Ano.length<4 || parseInt(Ano)<1900)
    {
            return false;
    }

    if (Mes==4 || Mes==6 || Mes==9 || Mes==11 || Mes==2)
    {
        if ((Mes==2 && Dia == 29 && !Bisiesto) || (Mes != 2 && Dia == 31))
        {
            return false;
        }
    }



  return true;
}

function isNumeric(cadena)
{
    var patron = /^\d+$/;
    return patron.test(cadena);
}