reset home folder permissions
1. Boot OS X Recovery by restarting the computer while holding the Command (⌘) and R keys.
2. When the Repair Utilities screen appears, select Utilities from the Menu Bar, then click Terminal.
3. In the Terminal window, type resetpassword and press Return.
4. The password reset utility window will appear. Do not select a new password.
Instead, click on the icon for your Mac's hard disk at the top. From the dropdown below it, select the user account with the problem.
5. At the bottom of the window, you will see Reset Home Directory Permissions and ACLs. Click the Reset button. Repeat for each User account with the problem.
The reset process may take a couple of minutes. When it finishes quit the programs and restart your Mac.
Depending on exactly what you did to your Mac's permissions the above may not help. If it does not, read and follow Apple Support Communities contributor Niel's User Tip: kmosx: I accidentally set a disk's permissions to No Access