This is really strange. None of the browsers on my machine can access this URL. But
dig _why.usesthis.com
returns the correct info.
According to Wikipedia, the use of underscores in hostnames is illegal, but many implementations ignore this. Anyway, the interview is mirrored here: http://viewsourcecode.org/why/#7
Looks like underscores are valid in /domain names/ but not in /host names/.
You'll see underscores used many times for SPF records and in Microsoft's Active Directory.
Also, when you use dig I'm pretty sure it manually recurses the name server hierarchy while an application will just connect to your local name server which might have its own policies.
According to Wikipedia, the use of underscores in hostnames is illegal, but many implementations ignore this. Anyway, the interview is mirrored here: http://viewsourcecode.org/why/#7