Use American spelling of "customization"

content/darkroom/organization/module-groups.md

@@ -60,7 +60,7 @@ This preset provides a minimal set of modules targeted as a starting point for b
 
 # _previous config_
 
-These presets are automatically generated for users who have upgraded from a version of darktable prior to 3.4. Where you have previously set up favourites or altered the _hidden_ flag on modules, these presets contains those customisations, retaining the legacy module groups (_previous config_ preset) or new module groups (_previous config with new layout_ preset).
+These presets are automatically generated for users who have upgraded from a version of darktable prior to 3.4. Where you have previously set up favourites or altered the _hidden_ flag on modules, these presets contains those customizations, retaining the legacy module groups (_previous config_ preset) or new module groups (_previous config with new layout_ preset).
 
 If favourites were created in prior versions these will remain available in an additional group:
 

content/preferences-settings/general.md

@@ -24,7 +24,7 @@ GUI controls and text DPI
 
 # CSS theme modifications
 
-In addition to selecting a pre-built theme you can also apply additional CSS customisations of your own to tweak the look-and-feel of darktable.
+In addition to selecting a pre-built theme you can also apply additional CSS customizations of your own to tweak the look-and-feel of darktable.
 
 Two different methods are provided for this:
 
@@ -50,7 +50,7 @@ create theme tweaks
 
 All of darktable's pre-built themes are provided as CSS files in `$DARKTABLE/share/darktable/themes/` (where `$DARKTABLE` is darktable's installation directory). The `darktable.css` theme contains the bulk of the code used to control the look-and-feel of darktable. A number of other themes are also provided but most of them use `darktable.css` as a base (by importing `darktable.css` using the `@import url` directive).
 
-If you choose to create your own custom theme file you are advised to follow a similar approach -- import one of darktable's existing theme files using `@import url` (this directive expects relative paths) and then apply your own customisations on top. You do not need to do this when using the CSS text box in the preferences dialog -- attempting to use `@import url` in the CSS tweaks text box will not work correctly.
+If you choose to create your own custom theme file you are advised to follow a similar approach -- import one of darktable's existing theme files using `@import url` (this directive expects relative paths) and then apply your own customizations on top. You do not need to do this when using the CSS text box in the preferences dialog -- attempting to use `@import url` in the CSS tweaks text box will not work correctly.
 
 Themes use the same basic CSS principles as in html browsers (with some minor exceptions -- see the [Gtk documentation](https://developer-old.gnome.org/gtk3/stable/chap-css-overview.html) for details):