http-headers Accept: (Request) Preference for one type over another
Example
Request:"http://example.com"
GET / HTTP/1.1 Host: example.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:53.0) Gecko/20100101 Firefox/53.0 Accept: text/html,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive
The client will accept all types of Content-Types but prefers text/html and application/xml
