Merge pull request #239777 from csmulligan/csmulligan-ciam-css

[CIAM] Add CSS reference (ADO-96058)

Author: ttorble

articles/active-directory/external-identities/customers/how-to-customize-branding-customers.md

@@ -31,7 +31,7 @@ You can also create user flows programmatically using the Company Branding Graph
 
 The default sign-in experience is the global look and feel that applies across all sign-ins to your tenant. The default branding experiences between the customer tenant and the default Azure AD tenant are distinct.
 
-Your Azure AD tenant supports Microsoft look and feel as a default state for authentication experience. You can [customize the default Microsoft sign-in experience](/azure/active-directory/fundamentals/how-to-customize-branding) with a custom background image or color, favicon, layout, header, and footer. You can also upload a custom CSS. If the custom company branding fails to load for any reason, the sign-in page will revert to the default Microsoft branding.
+Your Azure AD tenant supports Microsoft look and feel as a default state for authentication experience. You can [customize the default Microsoft sign-in experience](/azure/active-directory/fundamentals/how-to-customize-branding) with a custom background image or color, favicon, layout, header, and footer. You can also upload a [custom CSS](/azure/active-directory/fundamentals/reference-company-branding-css-template). If the custom company branding fails to load for any reason, the sign-in page will revert to the default Microsoft branding.
 
 Microsoft provides a neutral branding as the default for the customer tenant, which can be customized to meet the specific needs of your company. The default branding for the customer tenant is neutral and doesn't include any existing Microsoft branding. If the custom company branding fails to load for any reason, the sign-in page will revert to this neutral branding. It's also possible to add each custom branding property to the custom sign-in page individually.
 
@@ -51,7 +51,7 @@ The following image displays the neutral default branding of the customer tenant
 
 ## How to customize the default sign-in experience
 
-Before you customize any settings, the neutral default branding will appear in your sign-in and sign-up pages. You can customize this default experience with a custom background image or color, favicon, layout, header, and footer. You can also upload a custom CSS. 
+Before you customize any settings, the neutral default branding will appear in your sign-in and sign-up pages. You can customize this default experience with a custom background image or color, favicon, layout, header, and footer. You can also upload a [custom CSS](/azure/active-directory/fundamentals/reference-company-branding-css-template). 
 
 1. Sign in to the [Microsoft Entra admin center](https://entra.microsoft.com/).
 1. If you have access to multiple tenants, use the **Directories + subscriptions** filter in the top menu to switch to the customer tenant you created earlier.

articles/active-directory/external-identities/customers/toc.yml

@@ -280,6 +280,8 @@ items:
       href: reference-user-permissions.md
     - name: Group and application roles support
       href: reference-group-app-roles-support.md
+    - name: Company branding CSS template reference guide
+      href: /azure/active-directory/fundamentals/reference-company-branding-css-template
     - name: Help and support options
       href: ../../develop/developer-support-help-options.md?context=/azure/active-directory/external-identities/customers/context/customers-context
     - name: MSAL references