If you are running AdSense, be sure that you stay current with their terms of service. I was reading them again last night and found something I wasn't aware of before; AdSense ads can not be placed on parked domains. I should have realized that but it stuck out as something I'd missed. So, I thought I'd pull out some items from Google's AdSense TOS
[TOS = Terms of Service] as a reminder:
These are only a portion of the items you should be aware of and they are subject to change so keep an eye on the TOS:
-Do not put AdSense ads, search boxes, or AdLinks units on any non-content pages including on error, login, "thank you" or welcome pages.
-Do not place AdSense ads on chat pages.
-AdSense ads can't be placed on parked domains, pop-ups, pop-unders, or in any email. They are testing AdSense for email so an email option will hopefully be available soon.
-Do not place AdSense ads on pages created just for showing ads. Keep your AdSense ads on pages with quality content.
-Do not obscure any part of the AdSense ads with other page elements. For example, do not place an AdSense ad unit on your page and then cover up the part of the unit that says "Ads by Gooooooogle" to mask the fact that they are ads.
-Be sure that all ad elements, including the text and URL, are visible. For example, don't pick a URL color that matches your background color.
-For alternate AdSense ads (for the times there is no AdSense inventory for a spot), don't designate another AdSense unit as your alternate ad.
-Do not pre-populate an AdSense search box. For example, taking a high paying term and having it automatically display in the search field of a search box so all the visitor has to do is click the button to search. The visitor has to type the term in.
-If you are running AdSense ads, you may not run ads from other context targeted ad services. For example, when Yahoo! rolls out their AdSense alternative, you won't be able to run both on the same page at the same time.
-If you sell ads directly to advertisers, be sure your ads don't look just like a Google ad. They don't want confusion in the visitors mind as to what is their ad unit and what is yours.
-No AdSense ads on pages with MP3, video, news group or image results. It is interesting that as of today's date, Flickr, which is basically a big directory of images owned by Yahoo! displays Google's AdSense ads on some of the pages. If you'd like to see an example of Yahoo!'s alternative to AdSense, there were some in the lower left column of this page: http://www.flickr.com/photos/tags/work/
-Do not click your own ads. Make sure your spouse and kids know not to click on your own ads as well.
-Do not in any way encourage visitors to click your ads.
-If you sell your site, your AdSense account can not be transferred to the new owner.
-Do not modify the AdSense code Google provides in any way.
-Do not place a search box on a page with no other content relevant to your site.
-If your have Google's AdSense search boxes on your site, you can't run search boxes from other services. For example, you wouldn't be able to run a search box from goClick and AdSense on the same *site*. This one easily trips people up because Google generally seems to only exclude the use of competitors on a page by page basis. This specifically says *site*.
Again, this is NOT a complete list and is meant only as a refresher. If you ever have questions or are unsure if doing something would violate the TOS, send an email to: [email protected]
Also, an AdSense FAQ can be found here: https://www.google.com/support/adsense