function show_kontakt(kontakt){
  if(kontakt == "main"){
    document.getElementById("kontakt").style.visibility = "visible";
  }
  if(kontakt == "praha"){
    document.getElementById("praha_bottom").style.visibility = "visible";
    document.getElementById("praha_top").style.visibility = "visible";
    document.getElementById("kladno_bottom").style.visibility = "hidden";
    document.getElementById("kladno_top").style.visibility = "hidden";
  }
  if(kontakt == "kladno"){
    document.getElementById("praha_bottom").style.visibility = "hidden";
    document.getElementById("praha_top").style.visibility = "hidden";
    document.getElementById("kladno_bottom").style.visibility = "visible";
    document.getElementById("kladno_top").style.visibility = "visible";
  }
}

function change_image(){
  ukazka = randomnumber=Math.floor(Math.random()*3);
  ukazka ++;
  document.getElementById("ukazka").src = "gfx/ukazky/"+ukazka+".jpg";
  //alert("dd");
  /*if(ukazka < 3){
    document.getElementById("ukazka").src = "gfx/ukazky/"+ukazka+".jpg";
    ukazka ++;
  }else{
    document.getElementById("ukazka").src = "gfx/ukazky/"+ukazka+".jpg";
    ukazka = 1;
  }
  setTimeout("change_image()", 5000); */
}     

function checkform ( form )
{
  problem = "false";
  if (form.jmeno.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.prijmeni.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.telefon.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.ulice.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.obec.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.psc.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.typ.value == "") {
    problem = "true";
    /*form.email.focus();*/
  }
  if (form.typ.value == "Jiné") {
    if (form.info.value == "") {
      problem = "true";
    }
  }
  
  if(problem == "true"){
    alert("Všechna pole musí být vyplněna.\r\n Pokud vašemu požadavku neodpovídá žádná možnost, vyberte \"jiné\" a požadavek popište.");
    return false ;
  }
  
  return true ;
}