Google Section Targeting

How to keep my Adsense Ads on target to the theme of my Blog ?

Sometimes I noticed Adsense Ads is not targeted when it installed on a blog, because a blog is very dynamic, it can move to one topic to other topic

In Wordpress, we can have 2 option for targeting Adsense Ads on the theme of our blog :
1. Use this section and Ignore the rest
In this option we can ask Google Robot only use a certain section for his target on Adsense Ads
You can add this code:
<!- -google_ad_section_start- ->
Hi, Google !, please use this section for targeting the Adsense Ads
<!- -google_ad_section_end- ->

2. Ignore this section and use the rest
Or, insead of option 1, you can ask Google to use all section EXCEPT this section.
You can add this code:
<!- -google_ad_section_start(weight=ignore)- ->
Hi, Google !, Don’t use this section for targeting the Adsense Ads
<!- -google_ad_section_end(weight=ignore)- ->