Click on the "gallery index icon" on the left to go back to the gallery index.
Note: Don't use the "back button" on the browser to navigate though the gallery.

Click the "full-size icon" on the right to view images full-screen! Click again to get back to this screen.

Gallery Navigation: left to right
Gallery Index | Next Set | - Previous Image | Thumbnail Images | + Next Image | Previous Set | Play/Pause| Full-screen