Update http-response-codes.md

Author: jaesoni

articles/application-gateway/http-response-codes.md

@@ -147,10 +147,14 @@ nginx
 
 If the backend server is nginx or nginx ingress controller, and if it has upstream servers, ensure the value of `nginx:proxy_read_timeout` matches or does not exceed with the timeout set in the backend setting.
 
-## Scenarios
+## Troubleshooting Scenarios
+
+### "ERRORINFO_INVALID_HEADER" error in Access logs
+
+**Issue**: The [Access log](monitor-application-gateway-reference.md#access-log-category) displays an "ERRORINFO_INVALID_HEADER" error for a request, despite the Response code (serverStatus) being 200. In other cases, the backend server will return 500. 
 
-### Issue: The [Access log](monitor-application-gateway-reference.md#access-log-category) displays an "ERRORINFO_INVALID_HEADER" error for a request, despite the Response code (serverStatus) being 200.
 **Cause**: The client sends a header containing CR LF characters.
+
 **Solution**: Replace the CR LF characters with SP (whitespace) and resend the request to Application Gateway.