Situation #1 - Applying for a new AdSense Account
When you create a new blog on Blogger and want to apply for AdSense with it, you will probably find the "Earnings Tab" is not active, and you can't submit an application.
This is because the blog is either too new, or has too little content to be able to qualify for AdSense, so the ability to apply is on hold (by the Earnings Tab being temporarily disabled) until such time as the maturity of the blog (it's age) and the amount of contents on the blog deem it as being fit to apply with.
When the earnings tab is enabled, you'll be able to apply with your blog. This, however, does not mean your blog is approved yet, it just means that you can apply with it. Whether or not the blog is approved will not be decided until it goes through a 2-step approval process.
The first step allows you to login to an AdSense account and to place the code on your blog. Once you've placed the code on your blog, the second step will begin.
The second step is where AdSense will review your blog and all of it's contents to see if it's something suitable for them to monetize. During this time, you won't see any ads on your blog. You won't see any ads unless AdSense approves it during this second step. Once the review is complete (this review can take anywhere from a few days to a few weeks) AdSense will send you another email, but you may notice ads showing before you actually get the email.
So, when does it become enabled?
Well, that's open for discussion really. Nobody knows because there is no information posted about what will cause it to become enabled. Having spent enough time in the AdSense forum you come to the conclusion that it can take several months before that happens. If one thinks about it logically, in a couple of months, how much content would you post? The average blogger probably posts twice a week at least, so two posts a week times 8 weeks equals about 16 posts, but most of the time, what we're seeing is the blogs need more than that in terms of content amounts, unless the posts are very long, so shoot for somewhere around 20 to 30 posts. The more content in each post, the more likely you'd be accepted with a lower number of posts. (Don't add words just for the sake of adding words. The posts have to be useful.)
If your blog is almost a few months old, or is a few months old and you have at least that much content, you should be getting pretty close to seeing your Earnings Tab enabled. Unless ... well there is another requirement that Adsense has for just about all of the Asian countries, and that is the fact that sites should be six months old, so some of you may have to wait longer than a couple of months.
Situation #2 - Adding a Blogger Blog to a Fully Approved AdSense Account
This occurs when you already have an AdSense account that's approved to display ads on your own websites, or already approved to display ads on Blogger URLs (blogspot URL).
Even though your AdSense account is already approved for another blog, your new blog still has to qualify to display ads on it, so ... the earnings tab is disabled, the same as if you were applying for a new blog.
This makes sense because no advertiser wants their ads displaying on sites with one post, that's a few hours old. The idea is pretty much the same as in Situation #1 - when your blog is suitable (in terms of age and content amount) the Earnings tab will become active and you can link your blog to your already approved AdSense account.
You will not have to go through another review at that time. Your account is already approved, so the ads will begin to show once you can link it to your AdSense account.
Situation #3 - Your Blog uses a Custom Domain
In some cases, the Earnings tab may not be available when you want to apply because your blog is already using a Custom Domain. In this case, if your site is old enough, and has enough content you can apply at the AdSense homepage with your domain instead. Be aware that if your site is really new and hasn't much content, it's likely to be rejected, even if you can apply.
Your account will go through the same 2-step process as noted above in Situation #1. If it's approved and the ads begin displaying, the Earnings Tab should eventually become enabled, but even without the earnings tab, the ads will still work fine and still accrue earnings.
Situation #4 - You Already have an AdSense Account approved through YouTube or AdMob
You can't place AdSense ads on a blogspot URL if your account was approved through YouTube or AdMob. Not without upgrading that Host Account. And to upgrade that Host account, you can't use a blogspot URL. Please see "Applying for a Host AdSense Account Upgrade" on this page for instructions on how to upgrade.
posted by J. Gracey Stinson