Hopefully the Mods don't get too upset about this as I think that I need to be a little more specific than widgets.
I run several destination guides, one of which has seen a huge CTR decline over the last year or so. All of my other guides are doing fine - better CTR than ever.
I know that there are still plenty of advertisers, however I am seeing nothing but irrelevant Ads on my problem site.
The problem is this:
Instead of seeing Ads for "MyCityName Hotels", I am seeing Ads for "OtherCityName Hotels". This applies equally to all of the other categories; e.g. I am seeing "OtherCityName Car Hire" rather than Ads for car hire in my city.
Again, I know that there are still advertisers, as in many cases they are the same ones that I see on my other sites - just with the wrong destination.
The targeting is fine on nearly all the other sites - however I have noticed that another site dedicated to "MyCityName" also has the same very badly targetted Ads.
I'm starting to think that it's not my site at all, but rather that something is broken in Adsense.