var img_home_on = new Image();
var img_speaking_on = new Image();
var img_video_on = new Image();
var img_pbs_on = new Image();
var img_products_on = new Image();
var img_blog_on = new Image();
var img_press_on = new Image();
var img_contact_on = new Image();
						
img_home_on.src = 'images/nav_home_on.gif';
img_speaking_on.src = 'images/nav_speaking_on.gif';
img_video_on.src = 'images/nav_video_on.gif';
img_pbs_on.src = 'images/nav_pbs_on.gif';
img_products_on.src = 'images/nav_products_on.gif';
img_blog_on.src = 'images/nav_blog_on.gif';
img_press_on.src = 'images/nav_press_on.gif';
img_contact_on.src = 'images/nav_contact_on.gif';

function roll_on(theimg) {
	img_on = eval('img_'+theimg+'_on.src');
	document['btn_'+theimg].src=img_on;
}

function roll_off(theimg) {
	document['btn_'+theimg].src='images/nav_'+theimg+'.gif';
}