Warn if any content from another domain used in page.
SEO Tips for DNS Performance
|If a HTML page contains content from diffrent domains. As an example if page is on www.example.com and load an image from www.sample.com . The user client browser must resolve the www.sample.com to it's IP address (DNS Resolve) so it take time from client and down the load performance of page.|
Page contains Script and/or Style and/or Image from another domain