QuickLook is a quick view application that is part of OS X 10.5 Leopard. It allows you to quickly see images, videos, text and other files without actually opening them. To active Quick Look just select the file and press space.
While QuickLook can read many file types, there is one common file type it can't preview — compressed files. See the image above of how QuickLook previews a compressed file. Not much useful information.
When you copy and paste text using Apple-C / Apple-V you are not only copying the textual data but also the styling of the text. This is not a good thing most of the time as it would create a mix of different font types, colors, weights, etc. in your document and you have to manually reset to make it look consistent.
If you want to help a friend to fix a Mac or want to buy a used Apple machine you will need detailed and extensive information about the computer. The easiest and fastest way to create a document that can be emailed is to export a text document with all the details from System Profiler. Here are detailed instructions:
Open Applications/Utilities/System Profiler application
When you move between mail servers or you want to get rid of old email accounts in Mail.app, you should pay extra attention when deleting them.
When you remove the account not only the account details will be deleted but all the email messages that are associated with the account will be wiped too. These emails are gone forever. You can not retrieve them from the Trash.
Let's say you want to delete a backup from an external drive you don't need anymore. This backup will be millions of files if it includes all the system files. If you want to delete such large amount of files using the Finder's Empty Trash command it may take you hours.
A simple trick in Terminal will reduce the time by 40% to empty your trash significantly. Carefully enter this command: sudo rm -r