docs: Link to server-side form validation (vercel#67514)

docs/02-app/01-building-your-application/01-routing/05-error-handling.mdx

@@ -13,7 +13,7 @@ Errors can be divided into two categories: **expected errors** and **uncaught ex
 
 ## Handling Expected Errors
 
-Expected errors are those that can occur during the normal operation of the application, such as validation errors or failed API requests. These should be handled explicitly and returned to the client.
+Expected errors are those that can occur during the normal operation of the application, such as those from [server-side form validation](/docs/app/building-your-application/data-fetching/server-actions-and-mutations#server-side-form-validation) or failed requests. These errors should be handled explicitly and returned to the client.
 
 ### Handling Expected Errors from Server Actions