function formValidation(form){
  
  var bf = "";

  if (
    form.elements['jmeno'].value == "" || 
    form.elements['prijmeni'].value == "" || 
    form.elements['telefon'].value == "" || 
    form.elements['email'].value == ""
  ){
    bf += "Vyplňte všechny povinné údaje.\n";
  }
  
  if (form.elements['heslo'] && form.elements['hesloznovu']){
    if (form.elements['heslo'].value != form.elements['hesloznovu'].value && (form.elements['heslo'].value != "")){
      bf += "Zadaná hesla nesouhlasí nebo nejsou zadána.";
    }
  }
  
  if (bf != ""){
    alert(bf);
    return false;
  }
  else {
    form.submit();
  }
  
}


window.addEventListener ? window.addEventListener("load",cf_init,false) : window.attachEvent("onload",cf_init);

//default (strating) image
var current = 0;
//delay between slides
var delay = 5000;
//crossfade speed
var speed = 50;
//link to page
var buttonid = 'moreinfobtn';
//images container
var container = 'category';

var imgs = new Array();


function setLink(img){
  //copy link from image
  var btn = document.getElementById(buttonid);
  btn.href = img.getElementsByTagName('a')[0].href;
}

function setOpacity(obj) {
  if(obj.xOpacity>.99) {
    obj.xOpacity = .99;
    return;
  }
  obj.style.opacity = obj.xOpacity;
  obj.style.MozOpacity = obj.xOpacity;
  obj.style.filter = "alpha(opacity=" + (obj.xOpacity*100) + ")";
}

function cf_init() {
  if (!document.getElementById || !document.createElement) return;
  //get container object
  var cat = document.getElementById(container);
  //for stupid IE...
  catdivs = cat.getElementsByTagName('div');
  var im = 0;
  //get image objects
  for (var i=0; i<catdivs.length; i++){
    if (catdivs[i].className == 'image') imgs[im] = catdivs[i];
    im++;
  }
  maximg = imgs.length - 1;

  //set opacity of every image object to 0
  for(i=1;i<imgs.length;i++) imgs[i].xOpacity = 0;
  imgs[current].style.display = "block";
  imgs[current].xOpacity = .99;
  setLink(imgs[current]);
  
  //let's play :)
  setTimeout(cf_xfade,delay);
}

function cf_next() {
  cf_xfade();
}

function cf_prev() {
  cf_xfade_p();
}

function cf_xfade(order) {
  nIndex = imgs[current+1] ? current+1 : 0;

  setLink(imgs[nIndex]);

  cOpacity = imgs[current].xOpacity;
  nOpacity = imgs[nIndex].xOpacity;
  cOpacity -= .05;
  nOpacity += .05;
  
  imgs[nIndex].style.display = "block";
  imgs[current].xOpacity = cOpacity;
  imgs[nIndex].xOpacity = nOpacity;
  
  setOpacity(imgs[current]);
  setOpacity(imgs[nIndex]);
  
  if(cOpacity<=0) {
    imgs[current].style.display = "none";
    current = nIndex;
    var ordernext = setTimeout(cf_next,delay);
  } else {
    //clearTimeout(ordernext);
    var ordernext = setTimeout(cf_next,speed);
  }

}

function cf_xfade_p() {
  nIndex = imgs[current-1] ? current-1 : maximg;

  setLink(imgs[nIndex]);

  cOpacity = imgs[current].xOpacity;
  nOpacity = imgs[nIndex].xOpacity;
  cOpacity -= .05;
  nOpacity += .05;
  
  imgs[nIndex].style.display = "block";
  imgs[current].xOpacity = cOpacity;
  imgs[nIndex].xOpacity = nOpacity;
  
  setOpacity(imgs[current]);
  setOpacity(imgs[nIndex]);
  
  if(cOpacity<=0) {
    imgs[current].style.display = "none";
    current = nIndex;
    var ordernext = setTimeout(cf_next,delay);
  } else {
    //clearTimeout(ordernext);
    var ordernext = setTimeout(cf_xfade_p,speed);
  }

}