What is this U.V. artifact? So, I was just trying to really start mastering U.V. Unwrapping.  I was following this tutorial.  However, whenever I select the top of the mushroom and U.V. unwrap it: I get these strange artifacts in my mesh.  The overall screenshot can be seen here:  and you can see that I've highlighted the problem here: 

What causes this, and how do I get rid of it?  (I assume that I should.)  What effect will this have on my wraps if left alone?
It's hard to say exactly what the items are that are perplexing you. One possibility is that they may be one or more faces on the inside of your mesh that you created by accident. If this is the case, you might locate them by switching to wireframe mode. To see if it's a poorly unwrapped face, switch to textured mode in the 3D viewport, and move the point that is active in the UV editor window and see where the texture on the textured mesh moves.