It's Google advertising. I don't think IceinSpace has an option when it comes to this kind of thing. But, then again, I'm not a web developer or SEO specialist, so, don't know the in's and out's. : S
It's Google adSense, Google chooses relevant adverts to display based on it's analysis of page content. The most a site administrator like Mike can do is block specific adverts when they become aware of them, and that's a maintenance nightmare so I wouldn't expect Mike to bother excluding things like astrol*** adverts. Simply mentioning the word astrol*** in this thread will increase the chance of an advert of that nature being shown because Google will see the word mentioned more often and so think the adverts are more relevant.
Astrology sites probably pay google more to appear on "astronomy" sites like IceInSpace because they think they might get some interested people clicking on the links.
It's a very minor annoyance, nothing more. Like Roger said, trying to block them due to some moral frustration is more trouble than it's worth.
