function validate_email(field,alerttxt)
{
with (field)
  {
  apos=value.indexOf("@");
  dotpos=value.lastIndexOf(".");
  if (apos<1||dotpos-apos<2)
    {alert(alerttxt);return false;}
  }
}

function validate_form(thisform,alertemail,alerttour,alertparticipants,alertname)
{
var alerte = alertemail;
var alertt = alerttour;
var alertp = alertparticipants;
var alertn = alertname;

with (thisform)
  {
if (document.form1.name.value==null || document.form1.name.value=="")
  {
  alert( alertn );
  return false;
  }
  
if (validate_email(customer_mail,alerte)==false)
    {customer_mail.focus();return false;}
   
if ( document.form1.tour.selectedIndex == 0 )
    {
        alert ( alertt );
        return false;
    }
if ( document.form1.participants.selectedIndex == 0 )
    {
        alert ( alertp );
        return false;
    }
 else {return true;}
	
  }
}