var bildPfad = 'images/nav/'
	
	buttonOn = new Array();
	buttonOff = new Array();
	 
	 function preloadImages(){
					 if (document.images){
						 for (i =0; i<document.images.length;i++){
								
								if (document.images[i].name.indexOf('_button')!=-1){
									
										stopPoint = document.images[i].name.indexOf('_button');
										bildName=document.images[i].name.substring(0,stopPoint);
										
						
										
										buttonOn[document.images[i].name] = new Image();
										buttonOn[document.images[i].name].src = bildPfad + bildName + '_on.gif';
										
										buttonOff[document.images[i].name] = new Image();
										buttonOff[document.images[i].name].src = bildPfad + bildName + '_off.gif';
										
									
										
						
									}
								
								}
								if (selectedArea) lightUp(selectedArea);
							}
					}
	
	
	function lightUp(which){
			
			if (document.images){
				
				whichButton = which +"_button"
				newButton =  buttonOn[whichButton]
				if(buttonOn[whichButton]) document.images[whichButton].src=buttonOn[whichButton].src;
				
				return true;
				}
			}
			
		function darken(which){
			
			if ((document.images)&&(selectedArea!=(which + '_button'))){
				
				whichButton = which +"_button"
				newButton = buttonOff[whichButton]
				if(buttonOff[whichButton]) document.images[whichButton].src=buttonOff[whichButton].src;
			
				
				return true;
			}
			
		}
		
		var selectedArea='';