$(document).ready( function() {
	var j=0;
	$(".floor_img").each(function(i){
		var offImg="conference/img/img_01.jpg";
		var onImg="conference/img/img_0"+(j+1)+".jpg";
		if(j<6){
			$(this).mouseover( function() {
				$("#id-img1").attr("src", onImg);
		        $("#ImgrollColumn1st").show();
			});
			$(this).mouseout( function() {
		        $("#ImgrollColumn1st").hide();
			});
		}else{
			$(this).mouseover( function() {
				$("#id-img2").attr("src", onImg);
		        $("#ImgrollColumn2nd").show();
			});
			$(this).mouseout( function() {
		        $("#ImgrollColumn2nd").hide();
			});
		}
		j++;
	});
});