Often times I have seen programmers raise custom exceptions as, raise 'User is not authenticated', which is a very simple and readable approach but, does not have a well-defined structure to it. These are just strings littered all across your application and sometimes these strings get really really long. Ughh!
Concurrency and Parallelism are not the same thing. Understand how they differ and how it affects multi-threading in Ruby, across interpreters.
As it turns out IE9 has a limitation of 4095 selectors per CSS file. Selectors beyond that will be simply ignored.