How to reproduce:
- Install Reddit Enhancement Suite (RES)
- Make sure you installed Firefox's addon of synccit and logged in your synccit account.
- Go to https://www.reddit.com/r/gifs
- Try click that "view image" button:

What happened: if you click "view images (http://i.imgur.com/WxPcWD9.png [4] ), nothing happens: images don't expand.
What should happen: Images should all expand.
Note: It doesn't happen on Chrome with similar setup.