Why can you not see the stars sometimes?

i took accept this sometimes we wont see stars in some areas but in some areas we hava a nice view of stars i think its because of clouds and environmental chagens taken place in sky. Some Star Glaxies we can see in certain areas only. If you have a telescope u can understand what im saying...................

maybe you're at the wrong site or maybe the time you looked up, they are covered by clouds and when you got home, they appear because they are not already covered by clouds.

You said you couldn't see them when you came out of the store? If there are a bunch of streetlights, or a lot of lit buildings, signs, etc around, then it's almost impossible to see the stars because of the groundlight interfering. If there were no lights around, then it might just be you couldn't see the stars because of cloud cover. I live wayyyyy out in the country, I can see the stars every night unless there are heavy clouds in the sky. But when I go to the nearest town (which is a small town) I cannot see the stars because of groundlight interference. Think of it this way...if you are standing in your living room at night (with your lights on inside, and no lights outside) and it is dark outside, then you can't see outside at all. The lights in the room interfers with seeing outside. If you turn off the inside lights and then look out through the window, you can see outside fairly plainly. Same thing with city lights and not seeing the stars :-)