var backgroundOffset = 0;
var bgObject = eval('document.body');
var ScrollTimer = setInterval("scrollBG(300)", 170);

function scrollBG(maxSize) {
	backgroundOffset = backgroundOffset + 1;
	if (backgroundOffset > maxSize) {
		backgroundOffset = 0;
	}
	bgObject.style.backgroundPosition = "0" - backgroundOffset + 'px 0px';
}

function submitform()
{
  if(checkform(document.dotaznik)){
	document.dotaznik.submit();	
  }
}

function checkform(form) {
	
	if (form.email.value == "") {
		alert( "Vyplňte prosím emailovou adresu." );
		form.email.focus();
		return false ;
	}
   	var filter=/^.+@.+\..{2,3}$/
   	var address = form.email.value;
	   	if(filter.test(address) == false) {
	      alert('Neplatná emailová adresa.');
	      return false;
	   	}	
	  
  return true ;
}