function resetField()
{
	var arg = resetField.arguments, form = document.forms[ arg[0] ];
	if( form.elements[ arg[1] ].value == arg[2] )
	{
		form.elements[ arg[1] ].value = '';
	}
}

function estMail(ch)
{
    return ch.indexOf("@")!=-1 ? ch.substring(ch.indexOf("@")).indexOf(".")!=-1 : false ;
}

function checkform()
{
	var variable ="";
	if (document.forms['form1'].nom.value.length!=0)
	{
		if (document.forms['form1'].prenom.value.length!=0)
		{
			if (estMail(document.forms['form1'].email.value))
			{
				if (document.forms['form1'].datearrivee.value.length!=0)
				{
					return true;
				}
				else
				{
					variable="'Date d'arrivee'";
				}
			}
			else
			{
				variable="'Email'";
			}
		}
		else
		{
			variable="'Prenom'";
		}
	}
	else
	{
		variable="'Nom'";
	}
    window.alert ("le champs "+variable+" n'est pas correct ou vide !! ");
    return false;
}