There have been whole AdSense accounts bringing in $5000 per month banned for life from Google because of fraudulent clicks. If Google catches you clicking on your own AdSense ads, they can shut you down.
You won't get canned just for a single click, but if you're like me and tweak your site a lot it's only a matter of time before you click on one of those things by accident.
The way I keep this from happening is I temporarily block domain name Google's ads are served from. Once I'm finished editing my site I go back under hood and turn it back on.
Getting this setup will take you less than a minute.
First, find your HOSTS file.
Open Notepad. Go to File, and Choose Open.
If you have Windows 95, 98, or ME browse to folder "C:windows"
If you have Windows XP Home browse to folder "C:windowssystem32driversetc"
If you have anything else (Windows XP Pro, Windows 2000, NT, 2003, etc.) browse to folder: "C:winntsystem32driversetc"