As a general rule, the information sent by the browser to the server is the information that the server’s server uses to determine what to do on a given request. A server in a Web site may send back information to the browser that includes the user-agent string and perhaps other information that the server has determined is appropriate to transmit.
I don’t think this is something most developers want to hear. But hey, it’s free.
In some cases, you can also create a cookie in the browser that will expire and send a cookie back to the server. I’m not talking about using a cookie for something else, but simply sending the cookie back to the server will be a great way to build trust. The reason this is common is because we don’t want to have to worry so much about sending cookies back to the browser. We want to be able to send cookies back to the browser whenever we want.
The reason we want to send cookies is because we get the most out of cookies. We don’t want to have to worry about sending cookies back to the browser for the sake of cookies, but rather for the sake of cookies. We also want to be able to send cookies back to the browser whenever we want.