(function() {
	if (document.images) {
		// set image url
		var image_url = new Array();
		image_url.push("imgs/navigator/backArrowOv.png");
		image_url.push("imgs/navigator/nextArrowOv.png");
		image_url.push("imgs/navigator/tumbDownOv.png");
		image_url.push("imgs/navigator/tumbUpOv.png");
		image_url.push("imgs/navigator/map/grassGrass.png");
		image_url.push("imgs/navigator/map/grassGrassLand.png");
		image_url.push("imgs/navigator/map/grassGrassSea.png");
		image_url.push("imgs/navigator/map/grassGrassSea.png");
		image_url.push("imgs/navigator/map/grassLand.png");
		image_url.push("imgs/navigator/map/grassLandSea.png");
		image_url.push("imgs/navigator/map/grassNone.png");
		image_url.push("imgs/navigator/map/grassSea.png");
		image_url.push("imgs/navigator/map/grassSeaLand.png");
		image_url.push("imgs/navigator/map/landGrass.png");
		image_url.push("imgs/navigator/map/landGrassSky.png");
		image_url.push("imgs/navigator/map/landLand.png");
		image_url.push("imgs/navigator/map/landLandGrass.png");
		image_url.push("imgs/navigator/map/landLandSky.png");
		image_url.push("imgs/navigator/map/landNone.png");
		image_url.push("imgs/navigator/map/landSky.png");
		image_url.push("imgs/navigator/map/landSkyGrass.png");
		image_url.push("imgs/navigator/map/seaGrass.png");
		image_url.push("imgs/navigator/map/seaNone.png");
		image_url.push("imgs/navigator/map/seaSea.png");
		image_url.push("imgs/navigator/map/seaSeaGrass.png");
		image_url.push("imgs/navigator/map/skyLand.png");
		image_url.push("imgs/navigator/map/skyLandSpace.png");
		image_url.push("imgs/navigator/map/skyNone.png");
		image_url.push("imgs/navigator/map/skySky.png");
		image_url.push("imgs/navigator/map/skySkyLand.png");
		image_url.push("imgs/navigator/map/skySkySpace.png");
		image_url.push("imgs/navigator/map/skySpace.png");
		image_url.push("imgs/navigator/map/skySpaceLand.png");
		image_url.push("imgs/navigator/map/spaceNone.png");
		image_url.push("imgs/navigator/map/spaceSky.png");
		image_url.push("imgs/navigator/map/spaceSpace.png");
		image_url.push("imgs/navigator/map/spaceSpaceSky.png");
		
		for(var i=0; i < image_url.length; i++) {
			var preloadImage = new Image();
			//console.log(preloadImage);
			preloadImage.src = image_url[i];
		}
	}
})();