var selectedValue = 0;

function highlight(imgIndex)
{
	switch(imgIndex)
	{
		case 0:
			changeImages('intro', '/images/intro_roll.gif');
			changeImages('title', '/common/img/s.gif');
			break;
		case 1:
			changeImages('yr47_60', '/images/47_60_roll.gif');
			changeImages('title', '/images/47_60_title.gif');
			break;
		case 2:
			changeImages('yr70_80', '/images/70-80_roll.gif');
			changeImages('title', '/images/1970_title.gif');
			break;
		case 3:
			changeImages('ear_90', '/images/early_90_roll.gif');
			changeImages('title', '/images/early_90_title.gif');
			break;
		case 4:
			changeImages('mid_90', '/images/mid_90_roll.gif');
			changeImages('title', '/images/mid_90_title.gif');
			break;
		case 5:
			changeImages('yr2001', '/images/2001_roll.gif');
			changeImages('title', '/images/2001_title.gif');
			break;
		case 6:
			changeImages('pre', '/images/present_roll.gif');
			changeImages('title', '/images/present_title.gif');
			break;
		case 7:
			changeImages('cen21', '/images/21cen_roll.gif');
			changeImages('title', '/images/21cen_title.gif');
			break;
	}	
}

function unhighlight(imgIndex)
{
	switch(imgIndex)
	{
		case 0:
			changeImages('intro', '/images/intro_off.gif');
			break;
		case 1:
			changeImages('yr47_60', '/images/47_60_off.gif');
			break;
		case 2:
			changeImages('yr70_80', '/images/70-80_off.gif');
			break;
		case 3:
			changeImages('ear_90', '/images/early_90_off.gif');
			break;
		case 4:
			changeImages('mid_90', '/images/mid_90_off.gif');
			break;
		case 5:
			changeImages('yr2001', '/images/2001_off.gif');
			break;
		case 6:
			changeImages('pre', '/images/present_off.gif');
			break;
		case 7:
			changeImages('cen21', '/images/21cen_off.gif');
			break;
	}	
}

function snapBack(imgIndex, defaultTitle)
{
	unhighlight(imgIndex);

	switch(defaultTitle)
	{
		case 0:
			changeImages('title', '/common/img/s.gif');
			break;
		case 1:
			changeImages('title', '/images/47_60_title.gif');
			break;
		case 2:
			changeImages('title', '/images/1970_title.gif');
			break;
		case 3:
			changeImages('title', '/images/early_90_title.gif');
			break;
		case 4:
			changeImages('title', '/images/mid_90_title.gif');
			break;
		case 5:
			changeImages('title', '/images/2001_title.gif');
			break;
		case 6:
			changeImages('title', '/images/present_title.gif');
			break;
		case 7:
			changeImages('title', '/images/21cen_title.gif');
			break;
	}
}

function newImage(arg) {
	if (document.images) {
		rslt = new Image();
		rslt.src = arg;
		return rslt;
	}
}

function changeImages() {
	if (document.images && (preloadFlag == true)) {
		for (var i=0; i<changeImages.arguments.length; i+=2) {
			document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}
}

var preloadFlag = false;
function preloadImages() {
	if (document.images) {
		intro_over = newImage("/images/intro_roll.gif");
		yr47_60_over = newImage("/images/47_60_roll.gif");
		yr70_80_over = newImage("/images/70-80_roll.gif");
		ear90_over = newImage("/images/early_90_roll.gif");
		mid_90_over = newImage("/images/mid_90_roll.gif");
		yr2001_over = newImage("/images/2001_roll.gif");
		pre_over = newImage("/images/present_roll.gif");
		cen21_over = newImage("/images/21cen_roll.gif");
		preloadFlag = true;
	}
}
preloadImages();