function displayCenter(my_category) {	
			var category_array = new Array("convention","memo");
			var i = 0;
			while(category = category_array[i]) {
				category_style = document.getElementById(category+"_details").style;
				if(category == my_category) {
					category_style.display = "block";
					category_style.visibility = "visible";
				}
				else {
					category_style.display = "none";
					category_style.visibility = "hidden";
				}
				i++;
			}
		}

		function displayPhoto(photo_source,photo_id) {			
			document.getElementById(photo_id).src="images/"+photo_source;
		}