This is one of the stock OS X troubleshooting tips. It does actually solve some problems, and it doesn't do any harm.
Open the Disk Utility application in Applications : Utilities.
Select your hard disk name in the left panel. Select the First Aid tab in the right panel. Click the Repair Permissions button at the bottom.
It will take about 5 minutes, depending on the size of the disk. When the repair finishes, quit Disk Utility and restart the machine.