@shahsantosh, if you don't want to add that div tags, then here's a simple solution:
Add this code just above
]]></b:skin> in your template and it will automatically display the label where you place adsense ads. Means, if you add ads below your post, below comments or change the place in future, it will automatically find adsense ad and appear above them.
Note: If you want to dress up the label, just create a picture of this (http://s12.postimg.org/ccrmygu6l/Untitled.png) size and draw what you want!
And a big reason for adding this method is, if your visitor click on X (cross button), advertisement label will appear if you try div method but if you will try CSS method, advertisement label will get vanished if anyone click on X button.