Due to Tumblr's planned infrastructure upgrade, all Tumblr blogs will experience downtime on Saturday as a result. The planned downtime, according to Tumblr, will last a few hours. That's if everything goes well.
That's quite an inconvenience for all Tumblr users. Hopefully the benefits outweigh the frustration.
However, I tend to prefer my own stupidity for the reason why this site goes down.