window.onload = function preloadImages() {
	if (document.images) {
		about_us_on    		= new Image();
		about_us_on.src   	= strFiles + "/images/nav/about_us_on.gif";
		about_us_off     	= new Image();
		about_us_off.src 	= strFiles + "/images/nav/about_us_off.gif";	

		venues_on       	= new Image();
		venues_on.src   	= strFiles + "/images/nav/venues_on.gif";
		venues_off     		= new Image();
		venues_off.src 		= strFiles + "/images/nav/venues_off.gif";	

		contracts_on       	= new Image();
		contracts_on.src   	= strFiles + "/images/nav/contracts_on.gif";
		contracts_off     	= new Image();
		contracts_off.src 	= strFiles + "/images/nav/contracts_off.gif";	

		group_bookings_on     	= new Image();
		group_bookings_on.src 	= strFiles + "/images/nav/group_bookings_on.gif";
		group_bookings_off    	= new Image();
		group_bookings_off.src	= strFiles + "/images/nav/group_bookings_off.gif";	

		how_to_book_on       	= new Image();
		how_to_book_on.src   	= strFiles + "/images/nav/how_to_book_on.gif";
		how_to_book_off     	= new Image();
		how_to_book_off.src 	= strFiles + "/images/nav/how_to_book_off.gif";	

		contact_us_on 		= new Image();
		contact_us_on.src  	= strFiles + "/images/nav/contact_us_on.gif";
		contact_us_off     	= new Image();
		contact_us_off.src 	= strFiles + "/images/nav/contact_us_off.gif";
	}
	preloaded = true;
}

var preloaded = false;

function buttonon(buttonname) { 
	if ((document.images)&&(preloaded)) {
		document[buttonname].src = eval(buttonname + "_on.src");
	}
}
function buttonoff(buttonname) {
	if ((document.images)&&(preloaded)) {
		document[buttonname].src = eval(buttonname + "_off.src");
	}
}