function preload(img_src_array){
	var num_imgs = img_src_array.size;
	for(var i=0; i<num_imgs; i++){
		img = new Image();
		img.src = img_src_array[i];
	}
	
}


function rollover(img_name, img_src){
	if ( document.images )
	  {
	    document.getElementById(img_name).src = img_src;
	  }
}