It's called negative camber and it's usually a good thing to have. Gives you more grip in the corners.
However, make sure both wheels are equal. If only one wheel is at an angle (usually the passenger side) it means something isn't right with your suspension.
There was a thread here just a few days ago about a broken/rusted suspension ear. Which will result in a large amount of negative camber on just one side.
Andy
PS: If you look at my avatar picture, you can see the rear wheel has some negative camber. Any more than that and you may have a problem ...