Recorded Response URL is a new Web Test Request property that captures the final URL for a request after following all redirects. The Web test recorder automatically populates this field with the appropriate value. Query string parameters are ignored in the URL. If you modify the URL of a request or set Follow Redirects to false, you need to manually update the Recorded Response URL property.
Validate Response URL rule is a build-in test-level validation rule and it applies to all requests in a Web test. It validates that the response URL after redirects are followed is the same as the Recorded Response URL. It is added automatically after requests have been recorded. The primary purpose of this rule is to detect redirects to an error page.