What does a vertical brown line on a fingernail mean?

I get them from time to time but never know what they mean, they just appear from no where and grow out. its about 2mm long and towards the end of my nail.What does a vertical brown line on a fingernail mean?
If they come and go, then they are NOT a melanoma. However, they sound as if they are ';splinter hemorrhages';, which actually are small blood leaks under the nail plate, probably due to minor trauma to the nail plate area. Because of the architecture of the nail plate and the underlying blood vessels, a small blood leak will show up as a line. And, since yours are at the end of the nail plate, there is no worry that you are having an internal heart infection, which also can be seen as splinter hemorrhages, but not in that area of the nail plate.What does a vertical brown line on a fingernail mean?
could be:


Longitudinal Malanonychia


http://dermatology.about.com/library/bld鈥?/a>


or


Splinter Hemorrhage


http://www.nlm.nih.gov/medlineplus/ency/鈥?/a>
You've been scratching your bottom.