diff --git a/buildcache.py b/buildcache.py
index 03c5bb14..75a80c60 100755
--- a/buildcache.py
+++ b/buildcache.py
@@ -2,7 +2,7 @@
 #=======================================================================
 
 __version__ = '''0.0.01'''
-__sub_version__ = '''20131026130132'''
+__sub_version__ = '''20131219053320'''
 __copyright__ = '''(c) Alex A. Naanou 2011'''
 
 
@@ -50,6 +50,9 @@ CONFIG = {
 	'gid-source': 'original',
 
 	'base-ribbon': 0,
+	'tags': [
+		'unsorted',
+	],
 
 	'cache-image-name': '%(guid)s - %(name)s',
 
@@ -498,6 +501,7 @@ def build_images(path, config=CONFIG, gid_generator=hash_gid, dry_run=False, ver
 			'name': name,
 			'type': 'image',
 			'state': 'single',
+			'tags': config.get('tags', []),
 			'orientation': {
 					0: 0,
 					1: 0,
@@ -647,7 +651,8 @@ def build_data(images, path, config=CONFIG):
 # High-level API...
 #---------------------------------------------------------build_cache---
 def build_cache(path, config=CONFIG, gid_generator=hash_gid, 
-		report_progress=report_progress, dry_run=False, images_only=False, verbosity=0):
+		report_progress=report_progress, dry_run=False, images_only=False, 
+		verbosity=0):
 	'''
 
 	NOTE: when updating existing cache, this will re-sort the images.
@@ -832,6 +837,16 @@ def handle_commandline():
 	output_configuration.add_option('--base-ribbon',
 						default=CONFIG['base-ribbon'],
 						help='Base ribbon number (default: "%default").')
+	output_configuration.add_option('-t', '--tag',
+						action='append',
+						default=CONFIG['tags'][:],
+						help='add tag to each image (default: %default).',
+						metavar='TAG')
+	output_configuration.add_option('--notag',
+						action='append',
+						default=[],
+						help='do not add tag to images (default: %default).',
+						metavar='TAG')
 	output_configuration.add_option('--force-ascii', 
 						action='store_true',
 						default=False,
@@ -906,6 +921,9 @@ def handle_commandline():
 			'force-ascii': options.force_ascii,
 			})
 
+	# build the tags...
+	tags = config['tags'] = list(set(options.tag + config['tags']).difference(options.notag))
+
 	# a value from 0 through 2...
 	verbosity = options.verbosity
 	# bool...
diff --git a/ui/data.js b/ui/data.js
index 9c4182b1..52116eb6 100755
--- a/ui/data.js
+++ b/ui/data.js
@@ -13,12 +13,12 @@ var CONFIG = {
 
 	// Loader configuration...
 	//
-	//		load_screens	
-	// 	|<---------------------->|
-	// 	ooooooooooooXooooooooooooo
-	// 					 |<----->|<------------>|
-	// 						^	   roll_frame			  
-	// 		load_threshold -+
+	//						load_screens	
+	// 					|<---------------------->|
+	// 		ribbon:		ooooooooooooXooooooooooooo
+	// 									 |<----->|<------------>|
+	// 										^	   roll_frame			  
+	// 						load_threshold -+
 	//
 	// number of screens to keep loaded...
 	//
@@ -33,14 +33,28 @@ var CONFIG = {
 	// A threshold after which the image block ratio will be changed form 
 	// 1x1 to 'fit-viewer' in single image mode...
 	//
-	// this can be:
+	// This can be:
 	// 	- null					: feature disabled
 	// 	- number				: discrete threshold
 	// 	- array of 2 numbers	: two thresholds, in between the 
 	// 								image proportions will transition 
 	// 								gradually form square to screen
 	//
+	// When using array threshold, the gap between top and bottom must 
+	// be at least a couple of zoom_step_scale's.
+	//
 	// NOTE: the array format, threshold order is not important.
+	// NOTE: setting this to an integer may have a side-effect of making
+	// 		zooming of images win opposite proportions to the viewer 
+	// 		behave oddly on the threshold...
+	// 		...usually looking line the image getting a bit smaller for
+	// 		a step while zooming in, or the opposite, this is normal.
+	// NOTE: array of two integers produces a barely noticeable 
+	// 		side-effect of zooming being a bit uneven between the 
+	// 		threshold values.
+	// 		this is due to the same reasons as for "jumping zoom" 
+	// 		described above, and will be less noticeable the larger the
+	// 		gap between thresholds.
 	proportions_ratio_threshold: [ 
 		1.2, 
 		2.5