When you go cruising the web bit of information superhighway with your magic Internet Explorer (or something else if you have better taste), your browser often spills out bits of information about your setup which is then accessible to website authors if they so wish. This is how sites such as this one can tell you things about what browser you are using amongst other kind-of-private information.

This is because behind the scenes your web browser transmits various textual headers to the server hosting the webpage. At a minimum it has to transmit the name of the webpage it wants to download. This command looks something like:

In fact, if you are desperate to megageek it up, you can connect directly to (usually) port 80 of a webserver via telnet, type these commands in yourself, and see what the webserver sends to you. Other headers it might transmit include the name of your browser, what filetypes you want to receive and if you're going through a proxy. Some websites use that information to control some aspect of the site, for instance denying access to known spammer programs. Others, particularly a few years ago, will only let you read it if for instance you're using Internet Explorer. This is very naughty though and the Poorhouse would regard it more as an instance of bad or lazy coding to make a site that only works on one browser, and worse yet to actually deny others from even trying to interpret it.

If you're the owner or tester or a site where it would be useful to be able to modify a big pile of the headers from the webbrowser to see how it behaves, PureMango have made a nice PHP script to fake these headers much more easily than fiddling with customisable browsers or telnet type programs. You'll need your own PHP-enabled computer to host it on because it is a bit open to abuse to allow the public to use it from someone else's site, but you can test the features here. The site also contains a useful document on what the web browser headers mean and how to use them.