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 Accept-Language: en Accept-Encoding: gzip, deflate Connection: keep-alive
The client will only accept Content-Language of English.