How to Do Plus and Minus on a Mac

Check to see if you have the ± symbol on your Mac keyboard. Some Macbooks released in 2009 or later have the symbol on the keyboard above the 'TAB' key. Press 'Shift'+'§' to produce the '±' symbol. If you do not have this key, you can use the universal method.
Hold 'Shift' and then hold 'ALT' (Option).
Press the equals sign (=) key. The three-key combination will insert the ± symbol.
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How to Prevent the Rearrangement of Icons on an iPhone

Jailbreak your phone. There is no utility available within the iPhone itself that allows icons to be locked. There is also no available app on the App Store that provides this functionality. However, if you jailbreak your phone, you will have access to apps that will provide you with this feature. Despite the name, jailbreaking an iPhone is not illegal.
Download Springlocker or Lockdown from Cydia. As new apps are constantly being released, there may be other apps that can provide this feature in the future. As of November 2010, these are the two programs that will enable you to lock your icons.
Go into the 'Settings' of your iPhone if you installed Springlocker. There will be a Spring Locker option that gives you the ability to turn 'Lock Icons' on or off. Turn it on to prevent your icons from being accidentally moved or deleted in the future.
If you installed Lockdown, you can stop icons from being moved, and you can also stop them from being opened if you want to restrict access to certain apps on your phone. You can access this feature through the 'settings' on your iPhone. You must turn the 'Lock Icon Placement' option to 'On' to prevent icons from being rearranged.
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How to Find IPSW for Redsn0w 4.2.1 (3 Steps)

Download the appropriate 4.2.1 IPSW firmware file to your computer by clicking on Apple's link to the firmware file. Apple released three versions of this IPSW firmware file based on the type of iOS device you want to use with the firmware file.
Double-click the Redsn0w icon on your computer to launch the Redsn0w jailbreaking tool.
Select the iOS 4.2.1 IPSW firmware file you download to your computer when prompted to select the appropriate iOS 4.21. IPSW firmware file.
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