White Faces and Leveling

Hey guys! I recently managed to get Blender on my latest computer so I’m trying to get used to it on the Mac.

I have two questions.

My first one is when I’m doing character modeling I’ll occasionally notice that a face I’ve previously created in Edit Mode (Wireframe View) suddenly looks white. I don’t know why and it bugs the crap out of me and I want to get rid of it, but the only way I know how is to Erase it and then Undo. Is there some reason for why this is happening and is there a better way to be rid of it?

My second question is, as I’m doing modeling, my vertices that are on either side on my model occasionally end up unaligned, like the ones that should be going down the center of the front and back of the leg. I really would like to have them aligned, but unfortunately I know of no simple way to align them along the same axis besides trying to drag them as close together along the same axis as possible (which is really imprecise). I recall some tutorial said something about using zero to straighten them out, but I find that 0 hides my model (I have to click 1 to get it back). Is there some shortcut for doing this?

Thanks!

The lightened face marks the active face, which is important for some tools.

As far as straightening a line of vertexes, select them and scale them to zero along an axis (press the key corresponding to the axis after you press s to start scaling). For example, if you wanted to flatten them along the x axis, s -> x -> 0.

Alright, thanks a lot for the alignment, it helped a lot.

Sometimes I have those faces and sometimes I don’t. I must be unintentionally activating them, so is there some way to turn them off or avoid causing them to appear?