How to repair disk permissions on your system disk:

Choose Volumes > Repair Disk Permissions.
File permissions may get corrupted when applications quit unexpectedly, your system freezes or crashes, after power outages, and after installing third-party applications from .pkg files. Wrong file permissions may cause some applications, especially those that come with Mac OS X or other system software to behave strangely or stop working entirely.
If any of your applications aren’t working or exhibiting problems, try repairing disk permissions. This checks the permissions of Mac OS X system files and Apple software installed from .pkg installers, and repairs them if they’re wrong.
Choose Volumes > Repair Disk Permissions.
Important: Repair Disk Permissions is no longer available on Mac OS X 10.11 “El Capitan” and later. There the system automatically repairs disk permissions when running software updates.