diff --git a/ui/bookmarks.js b/ui/bookmarks.js
index 8abbe88f..8de85227 100755
--- a/ui/bookmarks.js
+++ b/ui/bookmarks.js
@@ -25,11 +25,11 @@ var BOOKMARKS_FILE_PATTERN = /^[0-9]*-bookmarked.json$/
 */
 
 var getBookmarked = makeMarkedLister(function(){ return BOOKMARKS })
-var getUnbookmarked = makeUnmarkedLister(function(){ return BOOKMARKS }) 
+var getUnbookmarked = makeUnmarkedSparseLister(function(){ return BOOKMARKS }) 
 
 var getBookmarkedGIDBefore = makeGIDBeforeGetterFromList(
 		function(){ 
-			return BOOKMARKS 
+			return compactSparceList(BOOKMARKS)
 		})
 
 
@@ -83,12 +83,14 @@ var toggleBookmark = makeMarkToggler(
 			// add a bookmark...
 			if(action == 'on'){
 				if(BOOKMARKS.indexOf(gid) == -1){
-					insertGIDToPosition(gid, BOOKMARKS)
+					//insertGIDToPosition(gid, BOOKMARKS)
+					BOOKMARKS[DATA.order.indexOf(gid)] = gid
 				}
 
 			// remove a bookmark...
 			} else {
-				BOOKMARKS.splice(BOOKMARKS.indexOf(gid), 1)
+				//BOOKMARKS.splice(BOOKMARKS.indexOf(gid), 1)
+				delete BOOKMARKED[BOOKMARKED.indexOf(gid)]
 			}
 
 			bookmarksUpdated()
@@ -99,10 +101,10 @@ var toggleBookmark = makeMarkToggler(
 //
 var nextBookmark = makeNextFromListAction(
 		getBookmarkedGIDBefore, 
-		function(){ return BOOKMARKS })
+		function(){ return compactSparceList(BOOKMARKS) })
 var prevBookmark = makePrevFromListAction(
 		getBookmarkedGIDBefore, 
-		function(){ return BOOKMARKS })
+		function(){ return compactSparceList(BOOKMARKS) })
 
 
 
@@ -116,7 +118,7 @@ var loadFileBookmarks = makeFileLoader(
 		BOOKMARKS_FILE_PATTERN, 
 		[[], {}],
 		function(data){ 
-			BOOKMARKS = data[0]
+			BOOKMARKS = populateSparceGIDList(data[0])
 			BOOKMARKS_DATA = data[1]
 		})
 
@@ -126,7 +128,7 @@ var saveFileBookmarks = makeFileSaver(
 		BOOKMARKS_FILE_DEFAULT, 
 		function(){ 
 			return [
-				BOOKMARKS, 
+				compactSparceList(BOOKMARKS), 
 				BOOKMARKS_DATA
 			] 
 		})
@@ -159,12 +161,21 @@ function setupBookmarks(viewer){
 
 	return viewer
 		.on('sortedImages', function(){
-			BOOKMARKS = fastSortGIDsByOrder(BOOKMARKS)
+			BOOKMARKS = populateSparceGIDList(BOOKMARKS)
 			bookmarksUpdated()
 		})
 		.on('horizontalShiftedImage', function(evt, gid, direction){
-			if(shiftGIDToOrderInList(gid, direction, BOOKMARKS)){
-				bookmarksUpdated()
+			var n = DATA.order.indexOf(gid)
+			var o = BOOKMARKS.indexOf(gid)
+
+			// move the marked gid...
+			BOOKMARKS.splice(o, 1)
+			BOOKMARKS.splice(n, 0, gid)
+
+			// test if there are any marked images between n and o...
+			var shift = compactSparceList(BOOKMARKS.slice(Math.min(n, o)+1, Math.max(n, o)))
+			if(shift.length > 0){
+				marksUpdated()
 			}
 		})
 }
diff --git a/ui/marks.js b/ui/marks.js
index 9f62b421..eed62b27 100755
--- a/ui/marks.js
+++ b/ui/marks.js
@@ -78,17 +78,10 @@ function makeMarkedLister(get_marked){
 	return function(mode){
 		var marked = get_marked()
 		mode = mode == null ? 'all' : mode
-		var gids = mode == 'all' ? getLoadedGIDs(marked) 
+		return mode == 'all' ? getLoadedGIDs(marked) 
 			: mode.constructor.name == 'Array' ? getLoadedGIDs(mode)
-			: typeof(mode) == typeof(123) ? getRibbonGIDs(mode)
-			: getRibbonGIDs()
-
-		if(mode == 'all'){
-			return gids
-		}
-		return gids.filter(function(e){
-			return marked.indexOf(e) >= 0
-		})
+			: typeof(mode) == typeof(123) ? getRibbonGIDs(marked, mode)
+			: getRibbonGIDs(marked)
 	}
 }
 
@@ -105,63 +98,71 @@ function makeMarkedLister(get_marked){
 // XXX with sparce lists this is trivial: get all the null indexes...
 function makeUnmarkedLister(get_marked, get_cache){
 	return function(mode){
+		mode = mode == null ? 'all' : mode
+
 		var marked = get_marked()
 		var cache = get_cache != null ? get_cache() : null
 
-		mode = mode == null ? 'all' : mode
 		var gids = mode == 'all' ? getLoadedGIDs() 
 			: mode.constructor.name == 'Array' ? getLoadedGIDs(mode)
-			: typeof(mode) == typeof(123) ? getRibbonGIDs(mode)
-			: getRibbonGIDs()
-		mode = mode == 'ribbon' ? getRibbonIndex() : mode
-
-		// get the cached set...
-		if(cache != null && mode in cache){
-			return cache[mode]
-		}
+			: typeof(mode) == typeof(123) ? getRibbonGIDs(marked, mode)
+			: getRibbonGIDs(marked)
 
 		// calculate the set...
 		var res = gids.filter(function(e){
 			// keep only unmarked...
 			return marked.indexOf(e) < 0
 		})
-		if(cache != null && typeof(mode) == typeof(123)){
-			cache[mode] = res
-		}
 
 		return res
 	}
 }
+// NOTE: this is about an order of magnitude faster than the non-sparse
+// 		version...
+function makeUnmarkedSparseLister(get_marked, get_cache){
+	// mode can be:
+	// 	- null			- default, same as 'all'
+	// 	- 'all'			- process all loases gids
+	// 	- 'ribbon'		- process curent ribbon
+	// 	- number		- ribbon index
+	// 	- Array			- list of gids
+	return function(mode){
+		mode = mode == null ? 'all' : mode
+
+		var marked = get_marked()
+		//var cache = get_cache != null ? get_cache() : null
+
+		var res = mode == 'all' ? 
+				DATA.order.slice()
+			: mode == 'ribbon' ? 
+				populateSparceGIDList(getRibbonGIDs())
+			: typeof(mode) == typeof(123) ? 
+				populateSparceGIDList(getRibbonGIDs(mode))
+			: mode
+
+		// for ribbon modes, remove non-ribbon marks...
+		if(mode == 'ribbon'){
+			marked = getRibbonGIDs(marked)
+		} else if(typeof(mode) == typeof(123)){
+			marked = getRibbonGIDs(marked, mode)
+			mode = 'ribbon'
+		}
+
+		// negate the list...
+		marked.forEach(function(e, i){
+			delete res[i]
+		})
+
+		return getLoadedGIDs(compactSparceList(res))
+	}
+}
 
 
 var getMarked = makeMarkedLister(function(){ return MARKED })
-var getUnmarked = makeUnmarkedLister(
+var getUnmarked = makeUnmarkedSparseLister(
 		function(){ return MARKED }, 
 		function(){ return _UNMARKED_CACHE })
 
-// these two are about 3 orders of magnitude faster than the above...
-// ...which is better I do not yet know...
-function getUnmarked_s0(){
-	var order = DATA.order
-	var res = []
-	for(var i=0; i < order.length; i++){
-		if(MARKED[i] == null){
-			res.push(order[i])
-		}
-	}
-	//return res
-	return getLoadedGIDs(res)
-}
-function getUnmarked_s1(){
-	var res = DATA.order.slice()
-	// XXX is it normal that .map() and .forEach() skip undefined values?
-	MARKED.map(function(e, i){
-		delete res[i]
-	})
-	//return compactSparceList(res)
-	return getLoadedGIDs(compactSparceList(res))
-}
-
 
 // XXX make this undefined tolerant -- sparse list compatibility...
 var getMarkedGIDBefore = makeGIDBeforeGetterFromList(