Well what do we have here? Newly available factory images for Android 4.0.4 (IMM76I) can now be obtained via the web for all yakju variants of the GSM version Galaxy Nexus. In addition, there’s a new build on the horizon, “takju”. These images are highly coveted as they can assist you in a time of need, such as when you brick the heck out of your phone rendering it useless. The images can also help you move from a non-yakju build to a yakju one seamlessly. You’ll need fastboot of course and some experience flashing images can’t hurt either. Also note that as Google has begun selling their Nexus device on the Play Store, recall that this is not the same model, it’s the takju build. Takju is Android 4.0.4 (IMM76I) with some optimization for supporting Google Wallet.
source: Google Dev Site