Catching up on some AdSense news, been pretty busy lately. The big news that will make some publishers very happy is that Google has increased the number of URLs you can add to the competitive ad filter from 200 to 500.

The AdSense competitive ad filter lets AdSense publishers exclude specific ads from appearing on their content sites. This exclusion is done by URL only, which some publishers think is too limiting. The URLs you enter into your filter are matched against the display and destination URLs of the AdWords ads that are to be displayed on your sites. Any ads whose URLs match one of the entries in your filter are not displayed on those sites.

The primary purpose of the competitive ad filter is to prevent direct competitors from bidding for advertising space on your sites. If your primary business is selling widgets and you have a blog about widgets, you typically don’t want someone else advertising widgets on that blog. The filter is the only tool you have to reject those ads.

A secondary purpose is to block inexpensive ads for “MFA” (made-for-AdSense) sites from appearing on your sites. This was a big deal a couple of years ago, but I don’t see many people talking about that now. Google did crack down on using AdSense arbitrage as a way of generating traffic to AdSense sites. (You can still do it, but only using carefully-targeted ads that directly relate to the content of your landing page.)

The ad filter is a manually-intensive process — you have to figure out which URLs you don’t want yourself, often only be looking at the ads you see on the site — and it’s not something that most AdSense publishers should worry about, but it’s there if you’re having some problems.

Unrelated note: My new blog, I’m Not In Marketing, premiered yesterday. If you’re a techie, check it out!