function emailCheck (emailStr) {

/* The following pattern is used to check if the entered 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. */

    alert("Indirizzo e-mail non corretto (controlla @ e i punti .)")

    return false

}

var user=matchArray[1]

var domain=matchArray[2]



// See if "user" is valid

if (user.match(userPat)==null) {

    // user is not valid

    alert("Il nome non sembra essere valido.")

    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) {

            alert("IP address di destinazione non valido!")

        return false

        }

    }

    return true

}



// Domain is symbolic name

var domainArray=domain.match(domainPat)

if (domainArray==null) {

    alert("Il nome del dominio non sembra essere valido.")

    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.

   alert("L' indirizzo deve terminare con le lettere del dominio e con le due del paese.")

   return false

}



// Make sure there's a host name preceding the domain.

if (len<2) {

   var errStr="Questo indirizzo manca del nome del dominio!"

   alert(errStr)

   return false

}



// If we've gotten this far, everything's valid!

return true;

}


function validate() {



/* CHECK Ditta */
    if (document.contatti.Ditta.value=="") {
    alert("Campo Ditta obbligatorio !")
    document.contatti.Ditta.focus();
    return false
    }

/* CHECK nome */
    if (document.contatti.Nome.value=="") {
    alert("Campo Nome obbligatorio !")
    document.contatti.Nome.focus();
    return false
    }

/* CHECK Cognome */
    if (document.contatti.Cognome.value=="") {
    alert("Campo Cognome obbligatorio !")
    document.contatti.Cognome.focus();
    return false
    }


/* CHECK Indirizzo */
    if (document.contatti.Indirizzo.value=="") {
    alert("Campo Indirizzo obbligatorio !")
    document.contatti.Indirizzo.focus();
    return false
    }

/* CHECK CAP */
    if (document.contatti.CAP.value=="") {
    alert("Campo CAP obbligatorio !")
    document.contatti.CAP.focus();
    return false
    }

/* CHECK Provincia */
    if (document.contatti.Provincia.value=="") {
    alert("Campo Provincia obbligatorio !")
    document.contatti.Provincia.focus();
    return false
    }

/* CHECK Telefono */
    if (document.contatti.Telefono.value=="") {
    alert("Campo Telefono obbligatorio !")
    document.contatti.Telefono.focus();
    return false
    }



/* CHECK email */

    if (emailCheck(document.contatti.email.value)==false) {
        document.contatti.email.focus();
    return false
    }


    return true
}