this answer至
this question，
Lachlan-Hunt写下列内容：
With HTML5,you can choose to use HTML-only Syntax,meaning that it is only compatible with being served and processed as text/html it is not well-formed XML. Or use XHTML-only Syntax,meaning that is is well-formed XML,but uses XML features that are not compatible with HTML. Or,you can write a Polyglot document,which is conforming and compatible with both HTML and XHTML processing (In principle,this is conceptually similar to writing XHTML 1.0 that conforms with Appendix C guidelines).
什么是Polyglot文件？
解决方法
多语言程序是一种有效于多种语言的程序。见
http://en.wikipedia.org/wiki/Polyglot_(computing)。
多语种(person)是流利的语言的人。
因此，这种情况下的多边形文档既是有效的HTML和XHTML。
显然，这个词源自古希腊语，由“π”，“多舌”，“多舌”，“pol”，“tongue”，“’”，“))”
