Each Application Pool runs with a single worker process (w3wp.exe).
From IIS 6, we can assign multiple worker process on a single application pool. This method is called Web Garden.
Many worker process can provide better performance and response time to your application.
There are some restriction to use web garden for your application. You must use "out proc" for Session Mode and "Session State Server" or "Sql-server session state".
If you use "in proc" for Session Mode your application not work correctly.

To create a web garden, right click on the Application Pool -> Advance Setting and set the value of Maximum Worker Process under the Process Model section.

With this simple eight steps, you can enable the http compression on IIS 6.
It is useful if your application has very hard pages, but the compression requires much cpu usage.

1. Open a command prompt, type net stop iisadmin and press ENTER.

2. Type cd c:\inetpub\adminscripts and press ENTER.

3. Type CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/GZIP/HcScriptFileExtensions "asp" "dll" "exe" "aspx" "asmx" and press ENTER.

4. Type CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/DEFLATE/HcScriptFileExtensions "asp" "dll" "exe" "aspx" "asmx" and press ENTER.

5. Type CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/GZIP/HcDynamicCompressionLevel "9" and press ENTER.

6. Type CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/DEFLATE/HcDynamicCompressionLevel "9" and press ENTER.

7. Type cscript.exe adsutil.vbs set W3SVC/ID/Root/WebServiceTG/DoDynamicCompression True and press ENTER. (ID is the identifier of the application that you can find on the coloumn Identifier of IIS Manager)

8. Type net start w3svc and press ENTER.