How to change IIS 6.0 Site ID to be incremental rather than randomly generated number (numeric string) 

With IIS 5.1 and previous versions, site identification numbers were incremental. For example, because the default Web site is created first, its site identification number is 1, and the next site to be created is identified as 2. When a new site is created on IIS 6.0, a site identification number is randomly generated 'using the name'  of the Web site. This ensures that all IIS 6.0 servers in a Web farm have a good chance of generating the same site identification number for sites of the same name.

To change Site ID to be incremental - Edit the below mentioned registry key.

Registry Path: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\InetMgr\Parameters

Data Type: REG_DWORD

Default Value: Key is not created by default, and therefore site identifiers are large, unique, randomly generated numbers.

Range: 0 - 1

You can create the IncrementalSiteIDCreation key at the path specified above, and set it to 1 to force IIS to use incremental site identification numbers.