From Design Reviver:

Grunge style is rough, rugged, torn, worn, and tattered. To most, these adjectives would describe something less than appealing, but in the hands of a talented web designer, elements possessing these qualities can be used to turn a web site into a work of art. So, if you are just getting started in grunge design or if you are already a pro, you should find the grunge freebies in this article to be very useful.

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