So here goes the list of all the Environment variables that are inbuilt and can be used with ur CGI script: Variable Name Value DOCUMENT_ROOT The root directory of your server HTTP_COOKIE The visitor's cookie, if one is set HTTP_HOST The hostname of your server HTTP_REFERER The URL of the page that called your script HTTP_USER_AGENT The browser type of the visitor HTTPS "on" if the script is being called through a secure server PATH The system path your server is running under QUERY_STRING The query string (see GET, below) REMOTE_ADDR The IP address of the visitor REMOTE_HOST The hostname of the visitor (if your server has reverse-name-lookups on; otherwise this is the IP address again) REMOTE_PORT The port the visitor is connected to on the web server REMOTE_USER The visitor's username (for .htaccess-protected pages) REQUEST_METHOD GET or POST REQUEST_URI The interpreted pathname of the requested document or CGI (relative to the document root) SC...