function update_opis(form) {
  str = form.opis.value
  maxdl=150;
  strlength = str.length
  
  if (strlength > maxdl ) {
    alert("Za długi tekst"); 
    document.form.opis.value=str.substring(0,maxdl);
  } else 
    charleft = maxdl - strlength

  form.charno_opis.value=charleft
 
}