No, this is not a real Sinatra error :).
This is the personal homepage of Elad Meidar, a web developer and an entrepreneur specializing in Ruby on Rails. I hang around in Israel, and i am currently having the best time of my life over at Fiverr.com
I am a proud member of RailsBridge, Helping new Rails developers get into our world and also contributed a few Patches to the Ruby on Rails core.
Mootools is awesome, but it still lacks some of the features that JQuery has when dealing with effects and some other not-so-important stuff.
Moo.rd is an excellent extension which implements some more features back to mootools. features such as some extra effects (finally, a mootools shake effect!), windows, sliders and more.
recommended, get it here.
You're seeing this error because I think it is funny.