Sorted:

Why can't I e-mail people ?-Collection of common programming errors

If the derivative of an equation is undefined at one point, what is happening at that point?-Collection of common programming errors

PhP Undefined Variable?-Collection of common programming errors

0x800a1391 – JavaScript runtime error: 'JSON' is undefined in IE 10-Collection of common programming errors

Struct is not visible to .cpp-Collection of common programming errors

“Undefined symbols for architecture x86_64:” when compiling lex and yacc-Collection of common programming errors

Does anyone knows another way to tell JSLint / JSHint what global variables are already defined-Collection of common programming errors

How to use form_for helper in rails?-Collection of common programming errors

Undefined Symbol ___gxx_personality_v0 on link-Collection of common programming errors

Rails ActiveAdmin : undefined method `find' for ActiveAdmin::Page:Class-Collection of common programming errors