line 14 column 7 - Warning: <center> isn't allowed in <tr> elements
line 13 column 5 - Info: <tr> previously mentioned
line 14 column 7 - Warning: missing </center> before <td>
line 10 column 3 - Info: missing optional end tag </dd>
line 12 column 5 - Warning: The summary attribute on the <table> element is obsolete in HTML5
line 14 column 7 - Warning: trimming empty <center>
line 21 column 3 - Warning: <center> element removed from HTML5
line 12 column 5 - Warning: <table> attribute "summary" not allowed for HTML5
Info: Document content looks like HTML5
Tidy found 6 warnings and 0 errors!

One or more empty elements were present in the source document but
dropped on output. If these elements are necessary or you don't want
this behavior, then consider setting the option "drop-empty-elements"
to no.

About HTML Tidy: https://github.com/htacg/tidy-html5
Bug reports and comments: https://github.com/htacg/tidy-html5/issues
Official mailing list: https://lists.w3.org/Archives/Public/public-htacg/
Latest HTML specification: https://html.spec.whatwg.org/multipage/
Validate your HTML documents: https://validator.w3.org/nu/
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Do you speak a language other than English, or a different variant of 
English? Consider helping us to localize HTML Tidy. For details please see 
https://github.com/htacg/tidy-html5/blob/master/README/LOCALIZE.md