Establish an Amazon S3 bucket, configure it to serve a static webpage, and upload custom error pages to the S3 bucket.

Set up an Amazon CloudWatch alarm to trigger an AWS Lambda function when the ALB health check indicates a failed Target.FailedHealthChecks response. The Lambda function should then adjust the ALB's forwarding rule to direct traffic to a publicly accessible web server.

Enhance existing Amazon Route 53 records with health checks and configure a fallback target for failed health checks. Adjust DNS records to direct traffic to a publicly accessible webpage.

Deploy an Amazon CloudWatch alarm to activate an AWS Lambda function upon detecting an Elb.InternalError in the ALB health check response. The Lambda function should alter the ALB's forwarding rule to redirect to a publicly accessible web server.

Configure a custom error response in Amazon CloudFront by setting up a CloudFront custom error page. Modify DNS records to redirect to a publicly accessible web page.