Why Public Service Ads are bad?

Google adsense has become a very popular tool for making money from your site by showing advertisements. But sometimes you see PSA - better known as Public Service Ads on your pages. These ads are displayed because adsense has not been able to find suitable ads for your page. Without commiting these 15 Adsense mistakes, here are some ways to remove PSA.
How to remove Public Service Ads?

Develop sufficient good content with keywords on your webpage related to the topic of interest. Google is a great fan of good content websites.
Ensure that META tags like ‘title’ & ‘description’ and the headings tags like h1, h2 etc. have content which matches the rest of your site. They are main ways google judges your pages content.
Add specific keywords in your text which will help the google bot to determine and understand the content of your website. Repeat related keywords which will better help to understand site content. Do not fill your page with simlar keywords, it might work against your favour.
Try to keep the entire website focussed on a particular theme, so that even if the content on a particular page is lesser, the ads wil show.
Do not place multiple ad units if there are not suffcient ads to display on all of them. Also Google TOS do not allow placing more than 3 ad units on a page.
Use section targeting - you can target an ad unit to a specific section of your blog, as well as block out irrelevant sections like navigational links. Useful to get more targeted ads.