function checkform(){
//Variables
	var reponse, msg, question;
	var listequestions = new Array(document.forms[0].Question1, document.forms[0].Question2, document.forms[0].Question3, document.forms[0].Question4, document.forms[0].Question5, document.forms[0].Question6, document.forms[0].Question7, document.forms[0].Question8, document.forms[0].Question9, document.forms[0].Question10, document.forms[0].Question11, document.forms[0].Question12, document.forms[0].Question13, document.forms[0].Question14, document.forms[0].Question15, document.forms[0].Question16, document.forms[0].Question17, document.forms[0].Question18,document.forms[0].Question19, document.forms[0].Question20);
//Messages
	if (location.href.indexOf('index-en')!=-1)
		msg = "Please, answer question ";
	else
		msg = "Svp, veuillez répondre à la question ";
//Validation
	for (j=0;j<listequestions.length;j++){
		question = listequestions[j]
		reponse=false;
		if (j!=17)//question18 texte ouvert ne pas valider
		{
			for (i=0;i<question.length;i++){
				if(question[i].checked){reponse = true;break;}
			}
			if (reponse != true){alert(msg + (j+1));return false;}
		}
	}
}