Update index.html

Co-authored-by: Daniel Murphy <[email protected]>

index.html

@@ -1283,7 +1283,7 @@ <h3>
           [=manifest/*_localized=] members contain a [=language map=] that
           defines [=localized values=] for the given [=localizable member=] in
           the application. The user agent SHOULD use the user's localization
-          settings to select the [=localized value=] whose language tag best
+          settings to select the [=localized value=] whose [=language tag=] key best
           matches the user's preference. When no such [=localized value=] is
           available, the default representation is used.
         </p>