An excellent place for most new publishers to begin understanding policy and issues that may cause invalid clicks is the "AdSense Policies: A Beginner's Guide" page in the AdSense Help Center, and well worth taking the time to read for some established publishers. You might be surprised at some of what you'll find on this page.
One of the first things AdSense mentions in the "Clicks and Impressions" section is that they monitor these very carefully. There's an unspoken idea there, and if you think about it long enough you might understand what that hidden message is.
If AdSense is monitoring clicks and impressions "very carefully", it's probably a good idea for you to also monitor these yourself - "very carefully".
Monitoring the activity on your website or blog is one of the ways you can help to head off a lot of ad clicks that AdSense may consider to be invalid. You monitor site activity using Google Analytics, and any third-party site analyzer that records IP addresses, visitor activity, and times, and if you pay for webhosting, most hosts will have some sort of server logs for your site. Now is the time to familiarize yourself with some of these - simply do a web search for website statistics or counters and read through some of those available. Select one that fits your needs and learn how it works, and put the necessary codes on your site. Keep copies of logs or statistics, because these will be useful in analyzing your site and monitoring your traffic.
When you analyze your stats there are things you should watch for:
- one visitor clicking multiple ads in one visit (1 or 2 ads, probably okay. 7-10 or more ads, probably not okay but don't panic, just report it - 30+ ads clicked by one person...start panicing and remove your website from the allowed sites list, also report the IP addresses and times to adsense)
- many visits coming from a single IP address. This can cause problems with Adsense if those visitors are also clicking ads.
- many visits coming from the same referrer and you don't know why. Check out the referrer and find out why the visitors are originating from that site. Someone posted your link to a blog or group, that's probably okay depending on the purpose of the group. Someone posting your link to a link farm or link exchange - not okay. Contact the site and get them to remove your link.
- visitors coming from your own IP address and clicking ads. Definitely not okay. Even if it isn't YOU, it is someone in your household. Or, if you use a wi-fi connection and don't lock it down, it could be anyone close enough to logon to the internet using your IP. Make sure you password-protect your wi-fi logon, and don't share it with anyone. You may also want to check your connections even if you are using cable or dial-up. We ran into a situation where a neighbour had cut another neighbour's cable near the pole and inserted a splitter box. The neighbour was then able to use the cable connection belonging to someone else without paying for the services...and causing the other neighbour to have enormous internet bills.
If you discover anything you find suspicious or unreasonable on your stats, then you will want consider reporting this instance to AdSense. Please, please don't go reporting single unidentified click - that's not what we're talking about here. And you don't need to report every single click you aren't certain about. If you pay attention to your site activity, you'll soon be able to recognize things that are unusual or out of the normal ranges of your site activity.
You can report these using the Invalid or suspicious activity form, found on this page in the Adsense help center.
On the "AdSense policies: a beginner's guide" page you'll also note a small paragraph about traffic: "Be aware of how your site is promoted". Read it carefully, and follow the links in that paragraph because you may find that reading will save you a great deal of grief.
While AdSense doesn't tell you that you can't promote your site, there are certain types of promotional opportunities that AdSense frowns upon - things like traffic exchanges and link farms whose sole purpose is to send people to your site to register impressions or clicks. If you are planning to buy any sort of advertising to grow your site, you'll need to be very careful about what you buy, where you buy it, and what your purpose is for purchasing it.
In any case, garnering traffic through purchases means the advertiser (in this case you if you are buying traffic/ads) who also uses AdSense must following the Google landing page quality guidelines given to AdWords advertisers, even though you may not be purchasing your advertising through AdWords. These guidelines include a quality component that says landing pages (ie: the page your advertisement leads to on your site) must contain:
- original and relevant content (so, don't advertise free websites if you aren't indeed giving away free websites on your site/page and don't have content copied from other sites or RSS feeds)
- AdSense lists things like making sure the purpose of your site is clear to visitors, and that your content is not copied from other sites.
- navigability - the navigation should be clearly displayed on your page and should be simple for visitors to find; all the links should work and go to the correct page.
The landing page guidelines are quite clear on the fact that originality is what they expect - "relevance and originality are two characteristics that define high-quality site content." I don't think they can be any clearer than that. Users should easily find what your advertisement states and they should be able to find that on your landing page, and you should not have content that is not original (created by you).
There are many other valuable hints on landing page quality for AdSense publishers who wish to use advertising to promote their websites: such things as browser behaviours, collection of personal information; using too many popups, popunders, floating box elements and the like; fast loading pages, portal or doorway pages, etc.
Here's where things may take a little twist. How does all of the above apply to publishers who are disabled for invalid activity? Almost any violation of policies, including those above, could widely be construed as invalid activity. If you are not in compliance with all policies that AdSense and Webmaster Guidelines list (and the Landing Page Quality Guidelines), then any earnings you accrue could be considered invalid. In otherwords, clicks on AdSense ads on pages that are not in compliance with policy could possibly be listed as invalid clicks.
Having an account disabled for invalid clicks doesn't necessarily mean AdSense thinks you've clicked your own ads - of course you may have, in which case you'd already know that you did. But for those publisher's who have no idea what these invalid clicks are (or where they came from), the email they receive is a rude awakening, and often comes much too late. Even if they are able to discover the cause, the chances of getting the AdSense account re-instated are almost nil.
Publishers should not only correct the issues listed by Adsense in the warning notice (throughout their entire site, not just on the page given as a reference), but should very carefully review their sites to ensure there are no other issues. Besides carefully studying the AdSense Program Policies and Webmaster Guidelines, if you have purchased traffic or signed up for free traffic, you'll want to consider the quality of that traffic as well. When it comes to traffic, all is not equal. Traffic from sources unacceptable to AdSense is worse than no traffic at all and can also lead to invalid clicks.
These are only a few of the possible causes for invalid clicks, but some that AdSense Publishers can exercise some control over.