何为XHTML??

http://www.w3.org/http://www.w3.org/1999/xhtmlhttp://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtdhttp://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtdhttp://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtdhttp://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtdhttp://validator.w3.org/check/refererhttp://