Regex Email validation

I use this

@”^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$”
regexp to validate the email

([\w\.\-]+) – this is for the first-level domain (many letters and numbers, also point and hyphen)
([\w\-]+) – …

Bad value X-UA-Compatible for attribute http-equiv on element meta

I have used the same meta that HTML5 Boilerplate is using, and the W3C HTML validator complains:
Bad value X-UA-Compatible for attribute http-equiv on element meta.

What is the minimum valid JSON?

I’ve carefully read the JSON description http://json.org/ but I’m not sure I know the answer to the simple question. What strings are the minimum possible valid JSON?
“string” is the string valid …