Clear Sky Chart FAQ
As in this does not show an image with colored blocks.
In all cases so far, when people have reported this problem, it's turned out to be their browser, a browser-plug-in, or some other software on their computer, whose job is to kill advertising.
Apparantly some ad-killers an popup-killers think that the clear sky chart images are advertising and so refuse to let you see them.
Try this test: If you can see a chart image in the red box:
Try turning your ad-killing software off. If that works, then you probably don't need to turn it off permanently. Most ad-killers can be told to exempt selected websites. Tell yours to except the domain cleardarksky.com