if (document.images) { 

top_nav_homeon = new Image();
top_nav_homeon.src = "images/top_nav_home_on.gif";

top_nav_homeoff = new Image();
top_nav_homeoff.src = "images/top_nav_home_off.gif";

top_nav_noteson = new Image();
top_nav_noteson.src = "images/top_nav_notes_on.gif";

top_nav_notesoff = new Image();
top_nav_notesoff.src = "images/top_nav_notes_off.gif";

top_nav_eventon = new Image();
top_nav_eventon.src = "images/top_nav_event_on.gif";

top_nav_eventoff = new Image();
top_nav_eventoff.src = "images/top_nav_event_off.gif";

top_nav_talkon = new Image();
top_nav_talkon.src = "images/top_nav_talk_on.gif";

top_nav_talkoff = new Image();
top_nav_talkoff.src = "images/top_nav_talk_off.gif";

top_nav_memberson = new Image();
top_nav_memberson.src = "images/top_nav_members_on.gif";

top_nav_membersoff = new Image();
top_nav_membersoff.src = "images/top_nav_members_off.gif";

top_nav_contacton = new Image();
top_nav_contacton.src = "images/top_nav_contact_on.gif";

top_nav_contactoff = new Image();
top_nav_contactoff.src = "images/top_nav_contact_off.gif";

}

function on(imagename) {
    if (document.images) {
		document[ imagename ].src = eval( imagename + "on.src" );
    }
  }
function off (imagename) {
	if (document.images) {
		document[ imagename ].src = eval( imagename + "off.src" );
	}
}