Hi, I want to jailbreak my iphone 3g, so please guide me in this issue. Thank you!

Hi,
Here are the steps to unlock the iphone 3g using ultrasn0w:

Step 1: First follow the complete step by step guide posted here to jailbreak iPhone 3GS or iPhone 3G on iPhone OS 3.1.3 firmware.

Step 2: Once your iPhone is jailbroken, start “Cydia” on your iPhone and touch on “Manage” tab on the bottom. Now touch on “Sources”
Note: T-Mobile users should disable 3G before installing ultrasn0w.

Step 3: Touch on “Edit” and then on “Add”. You will be prompted to enter a url source as seen in the screenshot below. Type “http://repo666.ultrasn0w.com” and touch on “Add Source”.
Cydia will now automatically update your sources by following a series of automated steps.

Step 4: Once the repository has been added successfully, Search for “ultrasn0w” in Cydia and install this application. The latest version 0.92 of this app will automatically unlock your iPhone so that you can use it with any carrier with proper carrier name/logo.

Step 5: Now simply restart your iPhone. You should now have a fully unlocked iPhone 3G/3GS on firmware 3.1.3.

Thank you!