Google AdSense has recently introduced the category filter feature for publishers. The category filter, along with other ad optimization features such as competitive ad filter can be used to effectively increase your Google AdSense income.
The category filter (accessed via AdSense Setup -> Ad Review Center) allows you to select up to five ad categories that you want to filter out so that these category ads will not appear on your AdSense blocks. This gives you an opportunity to filter out ad categories with very low earnings. The following picture gives you an idea on how low earnings, but high impressions ad categories can be filtered.
In addition to filtering low-earnings categories, you can use this feature to filter out rated (Sexually suggestive, for example) ad groups as well. Also, categories that are not relevant to your sites can be blocked, though Google would have already done a good job of serving context specific ads.
Disadvantages of using Category filtering
Though, it might sound like a killer feature, there is a catch here. The filtering happens on the entire AdSense account and not per site/blog where the same AdSense publisher account is used. Hence, if you use the Category filter those categories will stop appearing on all your sites. If you have blogs on multiple niches it may not be really effective always.
Competitive Ad Filter
The competitive ad filter, is yet another AdSense optimization feature that was introduced a while ago. You can use this feature to prevent up to 500 low earning ads (i.e. low EPS) from appearing on your site. Blocking an ad essentially means blocking the target URL where the click on the ad takes you. In order to find the target URL you may use the AdSense Preview Tool that works only on Internet Explorer.
As in the case of category filter, the competitive ad filter works at an account level and not at a domain level.
Hope Google remove these limitations soon enough so that our AdSense income can be further improved.
Happy Money Making!