When referencing CSS files in HTML files used with Design Manager CSS media queries are removed from the link tag.
Design Manager allows you to quickly implement your user experience in SharePoint but if you want to build a great public-facing website you should build the Master Page and Page Layouts yourself instead.
When building public-facing websites with SharePoint 2013 you should disallow anonymous users from overriding the Master Page on your website.
When building content aggregations with users’ information Content Search Web Part publishes account names in page source.
When building content aggregations for catalog content in cross-site publishing scenarios Content Search Web Part includes the original URL of the catalog item in the page source.