Thong Kuah questions

Thong Kuah answers

• Unique index when one of two columns is null
• Should I use my personal email in my ssh public keys?
• How to cancel evaluating a required Ruby file? (a.k.a. top-level return)
• find_or_initialize_by on has_many association causes duplicate error
• why 'rake test' is trying to connect to my development DB?
• Selenium WebDriver + Firefox 7.0.1 incompatibility
• Attribute saved in development but not in production
• Rails 3 - Make text field accept only numeric values
• How to ignore multiple classes using the :not selector?