IIS stands for Internet Information Services.
You can install it on your server as follows.
Windows 2008:
Server Manager - Roles - Add Role - Select "Web Server (IIS)" and process with the installation.
Windows 2003:
Go to Control Panel - Add/Remove Programs.
Select Add/Remove Windows Components.
Select Internet Information Services checkbox and follow the installation instructions.
Please note that you need to re-map .NET framework to the IIS after that.
See the knowledgebase article:
http://support.myeasyprojects.net/KB/a36/can-i-install-re-install-iis-after-installing-net-framework.aspx
Article ID: 39, Created On: 2/26/2008, Modified: 3/5/2012