function displayForm()
{
    document.getElementById('box_book').style.visibility = 'visible';
}
function closeForm()
{
    document.getElementById('box_book').style.visibility = 'hidden';
    document.getElementById('msg').style.visibility = 'hidden';
}
function sendForm()
{  
      var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
      if (!document.getElementById('desc').value)
      {
          document.getElementById('msg').innerHTML = "Wpisz \'Opinię\'";
          document.getElementById('msg').style.visibility = 'visible'; 
          return false;
      }
      else
      {
          if (document.getElementById('name').value == "")
          {
            document.getElementById('msg').innerHTML = "Podaj \'Imię i nazwisko/Nazwa firmy\'";
            document.getElementById('msg').style.visibility = 'visible';
            return false;
          }
          else
          {
               if (document.getElementById('email').value !="" 
                && !document.getElementById('email').value.match(filter))
              {
                document.getElementById('msg').innerHTML = "Nieprawidłowy email";
                document.getElementById('msg').style.visibility = 'visible';
                return false;
              }
              else
                    document.feForm.submit();
          } 
      }
}