function img_show(img)
{	var myWidth = 0, myHeight = 0;
	  if( typeof( window.innerWidth ) == 'number' ) {
	    //Non-IE
	    myWidth = window.innerWidth;
	    myHeight = window.innerHeight;
	  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
	    //IE 6+ in 'standards compliant mode'
	    myWidth = document.documentElement.clientWidth;
	    myHeight = document.documentElement.clientHeight;
	  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
	    //IE 4 compatible
	    myWidth = document.body.clientWidth;
	    myHeight = document.body.clientHeight;
	  }

	img.style.left = (myWidth-img.width)/2+"px";
	img.style.top = (myHeight-(img.height+20))/2+"px";
	img.style.visibility = "visible";
}

function img_hide(img)
{
	img.style.visibility = "hidden";

}

function menu_toggle(item)
{ var children = item.getElementsByTagName("ul");
  var opened = document.getElementById('menu_item_opened');
  if ((opened != undefined) && (opened != children[0])) //jestli jsme neklikli na tu samou polozku
  { opened.style.display = "none";
    opened.id="";
  };
  if (children[0].style.display != 'block') 
  { children[0].style.display = "block";
    children[0].id="menu_item_opened";
  }
  else
  { children[0].style.display = "none";
    children[0].id="";
  };
  
}