There is a “small” error in the Application Pool configuration of SP2010:
“Unfortunately when creating a Web Application, SharePoint 2010 uses the SharePoint only property Display Name for the STS application. The STS application is required as part of every SharePoint 2010 Web Application and lives at /_vti_bin/sts.
As the Web Application is being provisioned SharePoint uses the display name, SecurityTokenServiceApplicationPool. This of course doesn’t exist in IIS and so the loading of this application pool for each web application will fail every time IIS starts up. This will result in a 5048 Warning from WAS within the System Event Log (for each Web Application)”
Read more here: http://bit.ly/6paghi