preloads=new Array('about','projects','billholm','research','trips','grants','support','advisory');
images=new Array();
for(i=0; i<preloads.length; i++) {
	images[i]=new Image(); images[i].src="images/nav_"+preloads[i]+"_over.gif";
}

function rollOver(which) {
	if (document.images) {
		document.images[which].src="images/nav_"+which+"_over.gif";
	}
}

function rollOut(which) {
	if (document.images) {
		document.images[which].src="images/nav_"+which+"_off.gif";
	}
}