Definitions

content
The information requested, e.g. hypertext (HTML), pictures, video.
standard
Here: A specification about how the bytes of the content are to be interpreted and presented to the user. Preferably should be open and well-accepted. Both server and user-agent must agree on it.
server
The computer and the applications running on it, which provide the content over a network and are controlled (and usually owned) by the content provider.
user
The human requesting the content. The consumer.
agent
Somebody/-thing working for and representing another one
user-agent
The application running on the client which requests the content and presents it to the user. A web-browser is a user-agent for the web (http and HTML).
client
The computer, which runs the user-agent and stands in front of the user. It is controlled (and usually owned) by the user.

Description

The term "user-agent" can be taken literally: The application has been chosen by the user and can often be configured to the user's pleasure. It is free to present the content however the user chooses, within the range the standard allows.

Even in violation with the standard, if the user explicitly chooses so (if the latter is legal varies from country to country and depends on who you ask). However, the HTML standard (in which webpages are defined) is very lax and allows about every presentation.

You can view the server and client as 2 opposing parties.

History

There is a broad range of user-agents. Some are only capable to display text. The graphical browsers gave many choices to control the presentation of the page, e.g. disable images, alter colors, font sizes etc..

Present

Today, unfortunately, the biggest browser makers are at the same time content providers. This is of course a conflict of interest; it is as if your lawyer were paid by your opponent. The concrete consequences are that the choice of the user gets smaller and smaller, because content providers get more abilities to control the presentation without the user getting a chance to ignore them.

Even worse, this increased control by the content provider also often increases the risk of security breaches.

Beonex

Beonex tries to revert this trend. Beonex works for the user and only for the user. Beonex' credo is to give the user full control again. Beonex' credo is to create real

user-agents.

Disclaimer

I am not a lawyer. This is not legal advise. It should be taken as the personal opinion of the author, Ben Bucksch.