Fix 404 (#4228)

Author: SamyOubouaziz

serverless/functions/concepts.mdx

@@ -39,7 +39,7 @@ A CRON trigger is a mechanism used to automatically invoke a Serverless Function
 
 ## Custom domain
 
-By default, a generated endpoint is assigned to your Serverless resource. Custom domains allows you to use your own domain - see our [custom domain documentation](/serverless/functions/how-to/add-a-custom-domain-to-a-function) for full details.
+By default, a generated endpoint is assigned to your Serverless resource. Custom domains allows you to use your own domain - see our [custom domain documentation](/serverless/functions/how-to/add-a-custom-domain-name-to-a-function/) for full details.
 
 ## Endpoint
 
@@ -193,4 +193,4 @@ Triggers can take many forms, such as HTTP requests, messages from a queue or a
 
 ## vCPU-s
 
-Unit used to measure the resource consumption of a container. It reflects the amount of vCPU used over time.
+Unit used to measure the resource consumption of a container. It reflects the amount of vCPU used over time.