Google parses your content and than show's relevant ads. And each time your page is viewed you request Adsense server to generate relevant ads for you. But its not necessary that you always get relevant ads related to your content.
The highest paying ads are the ones about products and business advertisers. Other ads about a free website may not pay you as much of a money. So you need to optimize your content to get those ads.
Some of you may be writing about something which may not be suitable for Adsense ads and the ads generated will probably be the lowest paying ads. But you know that you can generate ads of your choice just by some Html entities which will only target the content you like and ignore the rest.
Targetting Specific Content For Ads
<!-- google_ad_section_start --> (Content Starts Here)
<!-- google_ad_section_start(weight=ignore) --> (Sentence To Ignore)
<!-- google_ad_section_end --> (End Of Sentence To Ignore)
<!-- google_ad_section_start --> (Start Of Content Again)
<!-- google_ad_section_end --> (End Of Content)
The above entites are used for targetting specific content for ads, and ignoring the rest. But remeber that you must add the section_end entity after each sentence to ignore or it won't work.
For Blogger :
If you want to target your Post Content In blogger than
Go to Edit HTML - Expand Widgets - Press CTRL + F and search for <data:post.body/>
Now replace it with this
<!-- google_ad_section_start -->
<data:post.body/>
<!-- google_ad_section_end -->
For Targetting Specific Ads For Non Adsense Suitable Websites :
Suppose you are running a local website, and you only get clicks from your own country. Than you won't get a good ad revenue. And also the ads displayed on your site might not be very appealing.
To change this you can add the
<!-- google_ad_section_start(weight=ignore) -->Make a list of your own keywords between the
Your Sites Body Section
<!-- google_ad_section_end -->
<!-- google_ad_section_start -->
Your Own Keywords Seperated By Commas
<!-- google_ad_section_end -->
Now your ads will be only concentrated on these keywords and you will get ads of your choice.
Remember that you won't get results immediately. It may take a week or a month for adsense to do this properly for you. Try to use this feature fairly by not violating the T.O.S of adsense or you get banned.

