One need to perform below mentioned steps to propagate the user permissions for a website:
1) Open IIS 6.0 Manager.
2) Expand local computer.
3) Click on websites.
4) Search and Right click on website for which one need to propagate the permissions.
5) Click on permissions.
6) New window will appear and click on Advance button.
7) Select the username and click on edit to select the permissions.
8) Select the check box.
9) Click on apply and one can see the permissions propagation window.
10) Click on ok to complete the process.