How to add html fragments, ads, java scripts, banners, advertismets on page/post

By using following plugin in your wordpress instance.
You can simply add advertisment content or any html fragment to the header or footer of post/page.
Or you can use widget to do same, main support of targeting will be in futured versions.

http://wordpress.org/extend/plugins/ads-content/

as example
http://www.zivot-vecny.cz
http://www.zonarelaxace.cz