title: Which http request headers are required for client?
body: <p>Which of the http request headers are required for a client to get the correct response from server?
  Does it depend on server back-end?</p>
  
  <p>I've come up with situations in  which setting all request headers(just like browser does) gave me improper responses and i had to cross some out.</p>
  
  <p>If all request headers are required, does it mean http helper libraries in programming languages set some default values? If not, is there a better solution than error-and-trail?</p>