function changeDisplay(div_id,if_,then_)
{
 var elem=document.getElementById(div_id);
 if (elem)
 { if (elem.style.display==if_) {elem.style.display=then_;}}
} 
function open_sub(SM_SHORT)
{

/*	if (akt_sub!=SM_SHORT) {
		 changeDisplay(akt_sub,'block','none');
		 changeDisplay(SM_SHORT,'none','block');
		 akt_sub=SM_SHORT;			   
	}*/

}