Inside AdSense- Ad Relevance and Targeting co

To follow up on our previous post about ad relevance and targeting, let's look at some other reasons why you may experience ad targeting issues on your site.
Have you blocked the AdSense crawler's access to your pages? The AdSense crawler is an automated program that scans your web pages and tracks content for indexing. Sometimes we don't crawl pages because the AdSense crawler doesn't have access to your pages, in which case we're unable to determine their content and show relevant ads. Here are a few specific instances when our crawler can't access a site:

If you use a robots.txt file which regulates the crawler access to your page. In this case, you can grant the AdSense crawler access by adding these lines to the top of your robots.txt file:

User-agent: Mediapartners-Google*
Disallow:

If the sites you place the ad code on are behind a login, our crawler won´t be able to access your site. To grant access to such pages, please follow these instructions. Also, be sure to regularly check your site diagnostics tool to be aware of any blocked pages.

Is your site language supported by AdSense? Check to make sure that your site has a substantial amount of text-based content in one of the languages supported by AdSense. When there's enough content, our technology detects the primary language of each of your pages and delivers relevant ads in the appropriate language, even if your site contains multiple supported languages.

The crawlers used by Google AdSense index content by unique URL. As a result, if the URL is the same regardless which language the user chooses to view the pages in, our system will only have the language version it received when indexing this URL. This means that we'll show ads according to the page our system has in its cache, which might not match the language the user is viewing the page in. In order to resolve this, we suggest either of the following:
Create separate directories for each language, such as http://www.site.com/en/index.html
Send GET variables (encoded user information appended to the end of the URL after the ? character) in the URL to determine which language should be shown such as for example http://www.site.com/index.php?lang=en

Do you see public service announcements (PSAs) on a site which previously showed paid ads before? 

If your AdSense account requires PIN or phone verification, you'll see a prompt in your account when you sign in. If you fail to verify your PIN or phone number (requirements vary depending on your location), then you may see PSAs on your site . If this is not your case, please visit our Help Center for further information.

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