function permute(on, off){
	document.getElementById('onglet_'+on).className = 'onglet_on';
	document.getElementById('onglet_'+off).className = 'onglet_off';
	document.getElementById(on).style.display = 'block';
	document.getElementById(off).style.display = 'none';
}
function select_format(id, key){
	document.getElementById('add_format').value = id;
        document.getElementById('key').value = key;
        document.getElementById('form_format').submit();
}

function rollover(trid){
   document.getElementById(trid).className='opacity';
}
function rollout(trid){
   document.getElementById(trid).className='off';
}
function suppr_cart(reference){
   document.getElementById('suppr_cart').value = reference;
   document.getElementById('form_delete').submit();
}
function select_paiement(paiement){
   document.getElementById('sel_paiement').value = paiement;
   document.getElementById('form_paiement').submit();
}
function valid_form(){
   if(document.getElementById("format_checked").value<document.getElementById("total_prod").value){ 
      alert("Vous n'avez pas rempli tous les formats de vos photographies");      
   } else if(document.getElementById("paiement").value == ''){
      alert("Vous devez choisir un mode de paiement");
   }else {
      document.getElementById("bon_commande").submit();
   }
}
<!--
//pass min and max -measured against window width
function P7_MinMaxW(a,b){
	var nw="auto",w=document.documentElement.clientWidth;
	if(w>=b){nw=b+"px";}if(w<=a){nw=a+"px";}return nw;
}
//-->