line 1 column 1 - Warning: missing <!DOCTYPE> declaration
line 6 column 1 - Warning: <a> attribute with missing trailing quote mark
line 6 column 1 - Warning: <a> escaping malformed URI reference
Info: Document content looks like HTML5
3 warnings, 0 errors were found!

URIs must be properly escaped, they must not contain unescaped
characters below U+0021 including the space character and not
above U+007E. Tidy escapes the URI for you as recommended by
HTML 4.01 section B.2.1 and XML 1.0 section 4.2.2. Some user agents
use another algorithm to escape such URIs and some server-sided
scripts depend on that. If you want to depend on that, you must
escape the URI by your own. For more information please refer to
http://www.w3.org/International/O-URL-and-ident.html

About HTML Tidy: https://github.com/htacg/tidy-html5
Bug reports and comments: https://github.com/htacg/tidy-html5/issues
Or send questions and comments to: https://lists.w3.org/Archives/Public/public-htacg/
Latest HTML specification: http://dev.w3.org/html5/spec-author-view/
Validate your HTML documents: http://validator.w3.org/nu/
Lobby your company to join the W3C: http://www.w3.org/Consortium