The maxim about the Internet is that content is king. While this holds true for AdSense publishers, there’s one important caveat: if it’s not text-based content, our crawler might not notice.

While we’re constantly working to improve our targeting technology, our crawlers need text to properly match ads to your pages. Although images, flash, and streaming video can help spice up a site, relying heavily on these sorts of elements will make it difficult for us to get a good read on what your site is about.

If your site uses a lot of these features, make sure you provide enough text-based content in one of our supported languages to effectively convey the topic of your site. If our crawler doesn’t find enough text, you may get poorly targeted ads or public service ads (PSAs). While we can't say the exact amount of text content that you'll need to receive targeted ads, we do recommend including complete sentences and paragraphs on your pages.

To improve your ad targeting, here are few other pointers:

• Use text in addition to images when possible. Please note that the crawler can't read text contained within images.
  
• If you use images, be sure to title them appropriately and provide descriptive ALT tags.
  
• Try imagining your site without pictures or dynamic content. This will give you a good idea of what our crawler reads. If you lack imagination, you can try turning the images off in your web browser.
  

Finally, it's important to keep in mind that the AdSense for content ads on your site are automatically determined. Though it's not possible to choose the ads that are placed on your site, including more text-based content will help make it possible for our system to target your site correctly.

Posted by Kent Sugarman - AdSense Publisher Support