The usual way to implement configuration settings in your website is trough a ASP.NET web.config file in your website. It can be placed in any folder in the website. When using Sharepoint Portal Server (SPS) Windows Sharepoint Services (WSS) you have to deal with several place in which web.config files exists and have to be configured.
Usually a web.config exists in the virtual server and in the layouts directory. I assume that everyone working with sharepoint technology knows what a virtual server is. If not read a SPS manual to know what I’am talking about. This layouts directory is available from all virtual servers and the web.config also off-course. The physical path of the config file looks something like:
c:\windows\program files\common files\microsoft
shared\webserver extensions\60\templates\layouts
When adding, for instance, key/value pairs or register the session state module in the httpHandler section you have to keep in mind what purpose these settings have. If you have an application available only within one virtual server and only installed in the virtual serves then you only have to update the virtual servers web.config. If you are planning to install web applications which have to operate throughout the SPS installation take care to put the right configuration settings in the right configuration file.