It seems like the site is being attacked. I noticed a couple of times that the "404 not found nginx" error and it loaded later but it seemed like loading at a slower rate.
- Maybe some group is opposed to the idea of Steemit.
- It is a competition against other coins in the market.
- Someone is pentesting for fun.
I did a little search and it looks like it also happened six days ago. There were even theft involved. I guess that explains the decline of Steem in Poloniex.