# File lib/premailer/premailer.rb, line 397 def is_xhtml? intro = @doc.to_html.strip.split("\n")[0..2].join(' ') is_xhtml = !!(intro =~ /w3c\/\/[\s]*dtd[\s]+xhtml/i) $stderr.puts "Is XHTML? #{is_xhtml.inspect}\nChecked:\n#{intro}" if @options[:debug] is_xhtml end