Save and/or quit your applications & doucuments
Go to Applications>Utilities Folder
Click Disk Utility
Click the Volumn (HD) that you want to check.
Click the Repair Disk Permissions button. (Don't worry about verifying)
At the bottom of window when the repairs have finished, you will see the “most important thing”:
Permission Repairs Complete
The previliges have been repaired or completed on the selected volumn.
Restart your computer (Optional).
Go to Applications>Utilities>Disk Utility and select your volume and then select Repair Permissions.
**Same directions are also in the OS Mac Help Menu.**
http://docs.info.apple.com/article.html?artnum=25751 About Disk Utility's Repair Disk Permissions feature
TIP-You should Repair Permissions:
After installing and/or updating an OS (Operating System).
After installing software.