function Hover_menu (num, on)
{    
      if (on)
      {
          document[num].src='images/menu/'+num+'_hover.jpg';
      }
      else 
      {
          document[num].src='images/menu/'+num+'.jpg';
      }
}
function openWindow(url,w,h,scrolls)
{
  leftVal = (screen.width-700) / 2;
  topVal = (screen.height-500) / 2;
  w = w +20;
  h = h+20;
  scrolls = scrolls == false ? 0 : 1;
  window.open(url, "Detail", "width="+w+",height="+h+",menubar=no,resizable=yes,statusbar=no,scrollbars="+scrolls+",left="+leftVal+",top="+topVal);
}
function openWindowSend(url,w,h,scrolls)
{
  leftVal = (screen.width-700) / 2;
  topVal = (screen.height-500) / 2;
  w = w +20;
  h = h+20;
  scrolls = scrolls == false ? 0 : 1;
  window.open(url, "Odeslat", "width="+w+",height="+h+",menubar=no,resizable=yes,statusbar=no,scrollbars="+scrolls+",left="+leftVal+",top="+topVal);
}
  function validate_castC(f){

    if( f.email.value == "" ) { email();  return false;}
	if( f.zprava.value == "" ) { zprava();  return false;}
	if (!f.email.value.match("^[_a-zA-Z0-9\.\-]+@[_a-zA-Z0-9\.\-]+[\.]{1}[a-zA-Z]{2,4}$")) {notValidEmail();  return false;}
  }
 

   function email(){ alert('Vyplňte prosím Váš email.'); }
   function zprava(){ alert('Vyplňte prosím zprávu.'); }
   function notValidEmail(){ alert('Vámi zadaná emailová adresa je neplatná.'); document.getElementById("email").value = ""; }