function have_pos (obj) {
   var curleft = curtop = 0;
   if (obj.offsetParent) {
      do {
         curleft += obj.offsetLeft;
         curtop  += obj.offsetTop;
      } while (obj = obj.offsetParent);
      return [curleft,curtop];
   }
}

function show_img (p, n, m) {

   for (i= 0; i < m; i++) {
      document.getElementById ('imag'+p+i).style.display = 'none';
      document.getElementById ('tapa'+p+i).style.display = 'block';
   }
   document.getElementById ('imag'+p+n).style.display = 'block';
   document.getElementById ('tapa'+p+n).style.display = 'none';

}


function valida_contacte (msg0, msg1, msg2, msg3, msg4) {

   alrt = new (Array);

   with (document.getElementById ('contacte')) {
      if ( /^\s*$/.test (observacions.value) ) {
         alrt.unshift ('- '+msg4);
         observacions.focus ();
      }
      if ( /^\s*$/.test (email.value) ) {
         alrt.unshift ('- '+msg2);
         email.focus ();
      } else {
         if ( ! /^[A-Za-z0-9\.+_-]+@[A-Za-z0-9\._-]+\.[A-Za-z]{2,6}$/.test (email.value) ) {
            alrt.unshift ('- '+msg3);
            email.focus ();
         }
      }
      if ( /^\s*$/.test (nom.value) ) {
         alrt.unshift ('- '+msg1);
         nom.focus ();
      }
   }

   if ( alrt.length > 0 ) {
      alert (msg0+'\n\n'+alrt.join ('\n'));
      return false;
   } else {
      return true;
   }

}