Can you add any request header when you request from a webpage?

Also, can yo开发者_开发知识库u SEND any header back? (return headers) when you run a web server?

Or, are headers limited?

Web pages are retrieved using the HTTP protocol. HTTP is text-based. Both, a client requesting and a server responding within a HTTP communication can add custom headers to the HTTP messages. Its up to the communicating parties how to process these. I would assume that an unknown header is dropped silently.