function valide_form (){
	if (document.form.first_name.value == ""){
		alert ("You forgot to write your first name");
		document.form.first_name.focus(); 
		return false;
	}
	if (document.form.last_name.value == ""){
		alert ("You forgot to write your last name");
		document.form.last_name.focus(); 
		return false;
	}
	if (document.form.message.value == ""){
		alert ("You forgot to write your message");
		document.form.message.focus(); 
		return false;
	}
	if (document.form.email.value == ""){
		alert ("You forgot to write your e-mail");
		document.form.email.focus(); 
		return false;
	}else{
		var arobase = document.form.email.value.indexOf("@"); var point = document.form.email.value.lastIndexOf(".");
		if((arobase < 3)||(point + 2 > document.form.email.value.length)||(point < arobase+3)){
			alert("Your e-mail is not valid !"); 
			document.form.email.value=""; 
			document.form.email.focus(); 
			return false
		}
	}
	if (document.form.email_2.value == ""){
		alert ("You forgot to write your confirm e-mail");
		document.form.email_2.focus(); 
		return false;
	}else{
		var arobase = document.form.email_2.value.indexOf("@"); var point = document.form.email_2.value.lastIndexOf(".");
		if((arobase < 3)||(point + 2 > document.form.email_2.value.length)||(point < arobase+3)){
			alert("Your confirm e-mail is not valid !"); 
			document.form.email_2.value=""; 
			document.form.email_2.focus(); 
			return false
		}
	}
	if (document.form.email.value!=document.form.email_2.value){
		alert("Your e-mail and your confirm e-mail are not identical!"); 
		document.form.email_2.value=""; 
		document.form.email_2.focus(); 
		return false
	}
	if (document.form.expertise.value == ""){
		alert ("You forgot to select your area of expertise");
		document.form.expertise.focus(); 
		return false;
	}
		
	return true;
}