Not all new Blogger blog owners understand why they are asked for their birthdate, when they setup a Blogger or Google account.
Some folks see this as a violation of their right to privacy, and enter a fake birthdate. Some real serious privacy enthusiasts might enter "01/01/01", just to get through the setup process - maybe intending to correct it, later.
Nobody entering "01/01/01", for one's birthdate, suspects that claiming such a birthdate makes them - in 2013 - appear to be 12 years of age. Unfortunately, 12 years is below the minimum age for owning a Blogger blog.
Since Blogger / Google tries to protect the young people on the Internet from inadvertently exposing themselves - or their families or friends - to unknown dangers, people who may appear to be of insufficient age are subject to having their Blogger / Google accounts, and Blogger blogs, deleted or locked.
If you entered a fake birthdate some time ago, and now find your account or blog locked or deleted, you need to prove your age to Google - and you should do this promptly.
The Google Accounts document Frequently Asked Questions about Google Account and Age Requirements explains how you do this. The process of verifying your age / birthdate is not convenient - and some privacy enthusiasts may claim that it too violates their privacy rights - but it is necessary, to let you correct your birthdate - when you are legitimately of legal age.
Now, you have to hope that you did not, intentionally or mistakenly, also provide a bogus email account as your Blogger / Google account name / recovery email address. The process of identifying yourself as the owner (former, nominally underage) of a given Blogger / Google account is easier to do, when you have access to the email account stated as the account recovery email address.
An Important Update
If you did not use a Blogger / Google account when you Followed this blog, years ago, you are probably not Following now . During the past...