All env previews in the envs page are broken both on Google Chrome 62.0.3202.62 and Firefox Quantum 57.0 (Ubuntu 16.04.3 LTS). Some examples:
Yes the media such as videos has been lost, and the setup of the site as a kind of competition with scores and leaderboards has been stopped.
The OpenAI project’s public developer face now appears to consist mainly of the (very useful) gym and universe open-source projects on Github, plus this forum. The remains of the old site is still useful for looking up descriptions of the environments.
There have been a couple of posts trying to start projects to reclaim the lost functionality, but nothing concrete posted yet such as an alternative site.