Flipped Faces and Direction

Two previews, under Orientation in the Preview list, that show which way the UVs lie.

Flipped Faces

Both views under Flipped Faces: one face folded over in red, the rest blue

Faces laid out folded over, against the rest of their island, show red; the rest are blue. A texture shows mirrored on a flipped face, and it overlaps the faces it folded over. The counts at the bottom right of the UV Layout say how many are flipped.

A face usually flips when a vertex has been dragged across its neighbors. Drag it back, Relax the island, or Flatten it again.

Direction

Both views under Direction: arrows pointing up the texture, on the model and in the layout

Arrows pointing up the texture, toward the top of the 0-1 square, moving the way they point. In the UV Layout, an island turned against the others stands out by its arrows. On the model, the arrows show which way a texture's top lies on each part, to keep wood grain, bricks or writing running the right way.

To straighten an island, see Flip and orient.