Here's a link:

http://rationalwiki.org/wiki/Astrology

In brief, there is no evidence from properly conducted trials that astrology can predict future events at a rate better than chance. In addition physics as we currently understand it precludes any possible effect on us from objects so far away.

Astrology can appear to work through a variety of cognitive biases or can be made to appear to work through various forms of trickery. For example when someone is majorly freaked out by the accuracy of a guess (and with a large enough population reading a guess it's bound to be accurate for some of them) that is much more memorable and much more likely to be shared with others than times when the prediction is obviously wrong. As such the availability heuristic might make you think that such instances are far more common than they actually are, while the actual frequency is entirely explicable by chance alone.