Blue arrow on mini map?

[onemeg]

Can anyone tell me what the blue arrow on the edge of the minimap is? It doesn't seem to be pointing towards the quest I have highlighted at all...I can't determine what it is pointing to! I tried just following it but came to a zone edge. (And for the record I am map impaired, it took me forever to realize that the orange arrow is "north", lol).

[Asterio]

It's a custom marker.
You probably clicked on the map (M) with your left mouse, which sets a custom mark, and didn't noticed. To remove it, simply click on the mark again.