We're getting a lot of inquiries from a lot of people who, for whatever reason, aren't happy with iOS 7 and want to downgrade to iOS 6 with the set of instructions we provided for the original beta. However, that was then and this is now. if you are on the public release of iOS 7 and you're reading this, you can no longer downgrade to iOS 6 at this time.
The directions we offered several weeks ago were for users that were running the beta version of iOS 7 before it was ever made available to the public. Once Apple released iOS 7 to everyone, they quickly stopped signing iOS 6 installs. This simply means that if you try and downgrade back to iOS 6, iTunes will produce an error message saying that you can't. Users typically still a message saying they aren't eligible for that specific build. You didn't do anything wrong during the downgrade process, it just means you're running a newer version, aka iOS 7, and Apple doesn't want you going to an older version.
This is common practice for Apple and something that they always do when they release a new version of iOS. We wish we could give you another option to get back to iOS 6 but we can't right now. If and when we have one, we promise we'll share!
If you've already tried downgrading back to iOS 6 from iOS 7 and got error messages, simply restore your iPhone back to iOS 7 to get everything back up and running again.