Sorted:

Why jsHint doesn't detect an error “is undefined”?-Collection of common programming errors

What are advantages of predefining variable in global scope?-Collection of common programming errors

Rails: Devise: Undefined Method `username'-Collection of common programming errors

float bits and strict aliasing-Collection of common programming errors

Scope of variably sized array-Collection of common programming errors

error: Only the original thread that created a view hierarchy can touch its views-Collection of common programming errors

when redirect gives an error “undefined”-Collection of common programming errors

linker error: undefined reference to `vtable of QGLViewer’-Collection of common programming errors

jshint functions with dots in the name-Collection of common programming errors

Ruby-on-Rails: Devise custom failure app problem-Collection of common programming errors