//button image names
var buttons = new Array("bt_ltpub", "bt_ybbasics", "bt_ybprograms","bt_ybextras","bt_ybcovers","bt_ybtools","bt_yblibrary","bt_otherprod");
var topLevelButtons = buttons.length;

var imgs = new Array;
for(i=0;i<topLevelButtons;i++){
	//preload images
	imgs[i] = new Array;
	imgs[i][0] = new Image;
	imgs[i][0].src = '/assets/images/menu/'+buttons[i]+'.gif';
	imgs[i][1] = new Image;
	imgs[i][1].src = '/assets/images/menu/'+buttons[i]+'_over.gif';
	imgs[i][2] = new Image;
	imgs[i][2].src = '/assets/images/menu/'+buttons[i]+'_pressed.gif';
}

var imgObj;
function over(imgNum) {

	//reset all images
	menuClosingFunction();

	//image object
	if(ns4) { imgObj = document.layers["navlayer"].document.images["b"+imgNum]; }
	else { imgObj = document.images["b"+imgNum]; }

	//change image
	imgObj.src = imgs[imgNum][1].src;

	//find position of image
	xPos = getRealLeft(imgObj);
	yPos = getRealTop(imgObj);

	//activate menu with returned co-ordinates
	if(menuReadyState) { activateMenu(imgNum,xPos,yPos+2+imgObj.height); }
	}

function menuClosingFunction() {
	//reset all images
	for(i=0; i < topLevelButtons; i++){
		if(ns4) { 
			imgObj = document.layers["navlayer"].document.images["b"+i]; 
		}
		else { 
			imgObj = document.images["b"+i]; 
		}
		imgObj.src = imgs[i][0].src;
	}
}