What's Changed

This topic describes important differences in default behavior and settings between IIS 4.0, IIS 5.0, and IIS 5.1.

For information about new features in IIS 5.1, see Features.

Administration

Programmatic Administration

Active Server Pages (ASP)

Registry

Security

Documentation

Administration

In IIS 4.0, applications could either be run in the same process as the Internet service or in a separate process. In IIS 5.0 and 5.1, applications can now be grouped into pooled processes for increased performance and improved scalability. For more information, see Application Protection in the About Applications topic.
The Application Mappings property sheet contains a list of Hypertext Transport Protocol (HTTP) verbs that will be processed by an application that is mapped to certain file types. This list of verbs represents a change from IIS 4.0. In IIS 4.0, the list contained verbs that were excluded, or not processed. This change was made to accommodate new HTTP verbs as they are added to the Protocol. For more information on application mappings, see Setting Application Mappings.
The location of custom error files has changed. For more information, see Enabling Detailed Custom Error Messages.
The Internet Service Manager is no longer accessible from the Start menu. To administer IIS, open the IIS snap-in.

Active Server Pages (ASP)

See Important Changes in ASP.

Registry

During an upgrade from a previous installation of IIS, the following registry keys will be removed:

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
\INetMgr
\InstalledBy

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \InetMgr
   \Parameters
    \AddOnTools
     \&Key Manager

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \INetMgr
   \Parameters
    \x

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \INetMgr
   \Parameters
    \AddOnServices
     \Gopher

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
\INetStp
\SetupID

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \Windows
   \CurrentVersion
    \URL
     \Prefixes
      \ftp

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \Windows
   \CurrentVersion
    \Setup
     \OC Manager
       \mts_mmc

HKEY_LOCAL_MACHINE\SOFTWARE
\Microsoft
  \Windows
   \CurrentVersion
    \Setup
     \OC Manager
      \Subcomponents
       \iis_w3samp
       \iis_doc_common
       \iis_doc_ismcore
       \iis_doc_pwmcore
       \iis_doc_asp
       \iis_doc_sdk
       \iis_doc_mm

Security

Many of the security features available in IIS 4.0 have been simplified in IIS 5.0 and 5.1, which have new security task wizards: the Permissions Wizard, the Web Server Certificate Wizard, and the CTL Wizard. With these three wizards, you can synchronize Web and NTFS security settings, obtain and install server certificates, and create and modify certificate trust lists. For more information, see Using the New Security Task Wizards.
Index this resource is now enabled by default.
Script source access, which allows access to the source code of scripts in ASP pages and other scripts, is new and is disabled by default. It is available only if either Read or Write permission is selected.
FrontPage Web, which allows administration of sites on your server by using FrontPage, is no longer set in the IIS snap-in. It is enabled by default.

Documentation

See Windows NT Option Pack Documentation.