function checkform(which) {

if (which.nom.value==''){
	alert("Veuillez préciser votre nom")
	which.nom.focus();
	return false;
	}  

if (which.email.value==''){
	alert("Veuillez préciser votre Email")
	which.email.focus();
	return false;
	}  

if (!CheckEmail(which.email.value)) {
   which.email.focus();
   return false;
}
if (which.msg.value==''){
	alert("Veuillez préciser votre message")
	which.msg.focus();
	return false;
	}  
return true;
}
function CheckEmail (emailStr) {
var emailPat=/^(.+)@(.+)$/
var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"
var validChars="\[^\\s" + specialChars + "\]"
var quotedUser="(\"[^\"]*\")"
var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/
var atom=validChars + '+'
var word="(" + atom + "|" + quotedUser + ")"
var userPat=new RegExp("^" + word + "(\\." + word + ")*$")
var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")
var matchArray=emailStr.match(emailPat)
if (matchArray==null) {
	alert("Adresse Email incorrecte")
	return false
}
var user=matchArray[1]
var domain=matchArray[2]
if (user.match(userPat)==null) {
    alert("Adresse Email incorrecte")
    return false
}

var IPArray=domain.match(ipDomainPat)
if (IPArray!=null) {
	  for (var i=1;i<=4;i++) {
	    if (IPArray[i]>255) {
	        alert("Adresse Email incorrecte")
		return false
	    }
    }
    return true
}

var domainArray=domain.match(domainPat)
if (domainArray==null) {
	alert("Adresse email incorrecte")
    return false
}

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) {
   alert("Adresse email incorrecte")
   return false
}
if (len<2) {
   var errStr="Adresse email incorrecte !"
   alert(errStr)
   return false
}
return true;
}