function emailCheck(emailStr)
{
var myEMailIsValid = true;
var myAtSymbolAt = emailStr.indexOf('@');
var myLastDotAt = emailStr.lastIndexOf('.');
var mySpaceAt = emailStr.indexOf(' ');
var myLength = emailStr.length;

// at least one @ must be present and not before position 2
// @yellow.com : NOT valid
// x@yellow.com : VALID
if (myAtSymbolAt < 1 ) {
myEMailIsValid = false;
}

// at least one . (dot) afer the @ is required
// x@yellow : NOT valid
// x.y@yellow : NOT valid
// x@yellow.org : VALID
if (myLastDotAt < myAtSymbolAt) {
myEMailIsValid = false;
}

// at least two characters [com, uk, fr, ...] must occur after the last . (dot)
// x.y@yellow. : NOT valid
// x.y@yellow.a : NOT valid
// x.y@yellow.ca : VALID
if (myLength - myLastDotAt <= 2) {
myEMailIsValid = false;
}

// no empty space " " is permitted (one may trim the email)
// x.y@yell ow.com : NOT valid
if (mySpaceAt != -1) {
myEMailIsValid = false
}

if (myEMailIsValid == true) {
return true;
}
else {
// alert("Votre email n'est pas valide.");
return false;
}

}


function ValideForm()
{

//nom
if(document.Formulaire.nom.value.length==0)
{
alert('Votre nom n\'est pas saisi !');
document.Formulaire.nom.focus();
exit;
}


//email
if(document.Formulaire.email.value.length==0)
{
alert('Votre email n\'est pas saisi !');
document.Formulaire.email.focus();
exit;
}


if (!emailCheck(document.Formulaire.email.value))
{
alert('Votre email n\'est pas valide !');
document.Formulaire.email.focus();
exit;
}


//usermessage
if(document.Formulaire.usermessage.value.length==0)
{
alert('Votre message est vide !');
document.Formulaire.usermessage.focus();
exit;
}


document.Formulaire.method = "POST";
document.Formulaire.action = "envoimail.php";
document.Formulaire.submit();

}