Dont even think of offering incentives for clicks, using automated clicking tools, or other deceptive software. Adsense is very smart to detect fraudulent clicks. Check the ads which appear on your pages by the Google Preview tool if required.
2. Never change the Adsense code. There are enough means of adsense optimization & customizations available to change the colour, background or border to suit your needs. Do whatever you want to do outside the code, never fiddle within the ad or the search code. They know it when you do. The search code has more limitations to colour and placement, but you should adhere to the rules. The code may stop working and violates the TOS.
3. Do not place more than 3 ad unit and 1 ad links or 2 adsense search boxes on any web page. Anyway, ads will not appear in those units even if you place more ad units. But this is the limit they set, so it is better to stick to it.
[MaHe]
