Updated this using the en.yml file in the ruby.git distribution for reference

* Numbers are now correctly formatted
 * Added source code comments
 * Finished error message translations

vendor/plugins/rails-i18n/locale/is.yml

@@ -1,22 +1,63 @@
 # Icelandic, by Ævar Arnfjörð Bjarmason <avarab@gmail.com>
 is:
-  support:
-    array:
-      sentence_connector: "og"
-      words_connector: ", "
-      two_words_connector: " og "
-      last_word_connector: " og "
-      skip_last_comma: true
+  number:
+    # Used in number_with_delimiter()
+    # These are also the defaults for 'currency', 'percentage', 'precision', and 'human'
+    format:
+      # Sets the separator between the units, for more precision (e.g. 1.0 / 2.0 == 0.5)
+      separator: ","
+      # Delimets thousands (e.g. 1,000,000 is a million) (always in groups of three)
+      delimiter: "."
+      # Number of decimals, behind the separator (1 with a precision of 2 gives: 1.00)
+      precision: 2
+
+    # Used in number_to_currency()
+    currency:
+      format:
+        # Where is the currency sign? %u is the currency unit, %n the number (default: $5.00)
+        format: "%u %n"
+        unit: "kr."
+        # These three are to override number.format and are optional
+        #separator: ","
+        #delimiter: "."
+        #precision: 2
+
+    # Used in number_to_human_size()
+    human:
+      format:
+        # These three are to override number.format and are optional
+        # separator: 
+        delimiter: ""
+        precision: 1
+      storage_units:
+        # Storage units output formatting.
+        # %u is the storage unit, %n is the number (default: 2 MB)
+        format: "%n %u"
+        units:
+          byte:
+            one:   "bæti"
+            other: "bæti"
+          kb: "KB"
+          mb: "MB"
+          gb: "GB"
+          tb: "TB"
 
   date:
     formats:
+      # Use the strftime parameters for formats.
+      # When no format has been given, it uses default.
+      # You can provide other formats here if you like!
       default: "%d.%m.%Y"
       short: "%e. %b"
       long: "%e. %B %Y"
+
     day_names: [Sunnudaginn, Mánudaginn, Þriðjudaginn, Miðvikudaginn, Fimmtudaginn, Föstudaginn, Laugardaginn]
     abbr_day_names: [sun, mán, þri, mið, fim, fös, lau]
+
+    # Don't forget the nil at the beginning; there's no such thing as a 0th month
     month_names: [~, janúar, febrúar, mars, apríl, maí, júní, júlí, ágúst, september, október, nóvember, desember]
     abbr_month_names: [~, jan, feb, mar, apr, maí, jún, júl, ágú, sep, okt, nóv, des]
+    # Used in date_select and datime_select.
     order: [:day, :month, :year]
 
   time:
@@ -28,6 +69,16 @@ is:
     am: ""
     pm: ""
 
+  # Used in array.to_sentence.
+  support:
+    array:
+      sentence_connector: "og"
+      words_connector: ", "
+      two_words_connector: " og "
+      last_word_connector: " og "
+      skip_last_comma: true
+
+  # Used in distance_of_time_in_words(), distance_of_time_in_words_to_now(), time_ago_in_words()
   datetime:
     distance_in_words:
       half_a_minute: "hálf mínúta"
@@ -62,20 +113,6 @@ is:
         one: "meira en 1 ár"
         other: "meira en {{count}} ár"
 
-  number:
-    format:
-      precision: 2
-      separator: "."
-      delimiter: ","
-    currency:
-      format:
-        unit: "kr"
-        format: "%n %u"
-    precision:
-      format:
-        delimiter: ""
-        precision: 4
-
   activerecord:
     errors:
       template:
@@ -84,8 +121,8 @@ is:
           other:  "Ekki var hægt að vista {{model}} vegna {{count}} villna."
         body: "Upp kom vandamál í eftirfarandi dálkum:"
       messages:
-        # inclusion: "er ikke inkludert i listen"
-        # exclusion: "er reservert"
+        inclusion: "er ekki í listanum"
+        exclusion: "er frátekið"
         invalid: "er ógilt"
         confirmation: "er ekki jafngilt staðfestingunni"
         accepted: "þarf að vera tekið gilt"