Check the markup (HTML, XHTML, …) of Web documents
I got the following unexpected response when trying to retrieve < http:https://upload.wikimedia.org/wikipedia/commons/4/4f/Flag_of_Cameroon.svg >:
500 No Host option provided
If you made recent changes to your domain name (DNS) configuration, you may also want to check that your domain records are correct , or ask your hosting company to do so.