Howto: How to downgrade 5.0.1 to 4.3.3 / 4.3.5 - iPhone 4, 3GS, iPod Touch 4G, 3G, iPad:

Step 1: Make sure that you have downloaded the version of iOS
which you gonna downgrade to (4.3.5, 4.3.3 or any iOS version), you can
download any iOS firmware from our library - Click Here.

Step 2: Navigate to :
Windows Users: Windows > System 32 > drivers > etc
Mac Users : etc

Open hosts file with the text editor then add the following code to the end of the file :

74.208.105.171