There are a number of so called "environment" variables that are known and possibly logged whenever you access a page on the WWW. These variables and their values when you accessed this page are shown below. The variable name is on the left, its value on the right.
UNIQUE_ID=TzeqOdh3hEIACAPMtSMAAAAb HTTP_X_CC_ID=ccc04-01 HTTP_HOST=paulbourke.net HTTP_USER_AGENT=CCBot/1.0 (+http://www.commoncrawl.org/bot.html) HTTP_ACCEPT=text/html,application/xhtml+xml,text/xml;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 HTTP_ACCEPT_LANGUAGE=en-us,en;q=0.5 HTTP_ACCEPT_ENCODING=gzip HTTP_ACCEPT_CHARSET=ISO-8859-1,utf-8;q=0.7,*;q=0.7 HTTP_CONNECTION=close HTTP_CACHE_CONTROL=no-cache HTTP_PRAGMA=no-cache PATH=/sbin:/usr/sbin:/bin:/usr/bin SERVER_SIGNATURE= SERVER_SOFTWARE=Apache SERVER_NAME=paulbourke.net SERVER_ADDR=216.119.132.66 SERVER_PORT=80 REMOTE_ADDR=38.107.179.236 DOCUMENT_ROOT=/home/pbourke/public_html SERVER_ADMIN=webmaster@paulbourke.net SCRIPT_FILENAME=/home/pbourke/public_html/oldstuff/wwwknow/index.html REMOTE_PORT=49351 GATEWAY_INTERFACE=CGI/1.1 SERVER_PROTOCOL=HTTP/1.1 REQUEST_METHOD=GET QUERY_STRING= REQUEST_URI=/oldstuff/wwwknow/ SCRIPT_NAME=/oldstuff/wwwknow/index.html DATE_LOCAL=Sunday, 12-Feb-2012 07:02:01 EST DATE_GMT=Sunday, 12-Feb-2012 12:02:01 GMT LAST_MODIFIED=Sunday, 20-Feb-2011 05:46:56 EST DOCUMENT_URI=/oldstuff/wwwknow/index.html USER_NAME=pbourke DOCUMENT_NAME=index.html