function show(dropdown_id)
{
	pfeil=dropdown_id+"_pfeil";
	dropdown=document.getElementById(dropdown_id); 
	dropdown_style = dropdown.style;
	
	switch(dropdown_style.display) 
	{	
		case "block":
			dropdown_style.display = "none";
			document.images[pfeil].src='grafiken/menu_pfeil.gif';	
			break;

		case "none":
			dropdown_style.display = "block"; 
			document.images[pfeil].src='grafiken/menu_pfeil2.gif';	
	}	
}