function hideAll() {
 darken('name0');
 darken('name1');
 darken('name2');
 darken('name3');
 darken('name4');		
 var blok;
 blok = document.getElementById('prepni01');
 blok.style.display = "none";
 blok = document.getElementById('prepni02');
 blok.style.display = "none";
 blok = document.getElementById('prepni03');
 blok.style.display = "none";
 blok = document.getElementById('prepni04');
 blok.style.display = "none";
 blok = document.getElementById('prepni05');
 blok.style.display = "none";
}

function showInfo(nameInfo, nameHelp) {
 hideAll();
 lighten(nameHelp); 
 var blok = document.getElementById(nameInfo);
 if (blok != null) {
   blok.style.display = "block";
 }
}