if (document.images)
{
header_buildingnav = new Image;
header_buildingnav_roll = new Image;
header_schoolnav = new Image;
header_schoolnav_roll = new Image;
header_citynav = new Image;
header_citynav_roll = new Image;
header_publicnav = new Image;
header_publicnav_roll = new Image;

header_buildingnav.src = "image/nav/header_building.jpg";
header_buildingnav_roll.src = "image/nav/header_building_roll.jpg";
header_schoolnav.src = "image/nav/header_school.jpg";
header_schoolnav_roll.src = "image/nav/header_school_roll.jpg";
header_citynav.src = "image/nav/header_city.jpg";
header_citynav_roll.src = "image/nav/header_city_roll.jpg";
header_publicnav.src = "image/nav/header_public.jpg";
header_publicnav_roll.src = "image/nav/header_public_roll.jpg";
}

else
{
header_building = "";
header_building_roll = "";
header_building.home.src = "";
header_school = "";
header_school_roll = "";
header_school.home.src = "";
header_city = "";
header_city_roll = "";
header_city.home.src = "";
header_public = "";
header_public_roll = "";
header_public.home.src = "";
}