The Last of the Parsing Quirks

I implemented a single quirk for HTML5 parsing yesterday.

March 1995: Netscape 1.1 beta 1 is released with table support. Table closes a paragraph implicitly.
August 1995: Internet Explorer 1.0 is released. Table does not close a paragraph.
May 1996: The IETF publishes experimental RFC 1942 which says that table is block level content like paragraphs (i.e. closes paragraph implicitly).
January 1997: The W3C publishes HTML 3.2 with a DTD that makes tables close paragraphs implicitly in an SGML parser.
December 1997: The W3C publishes HTML 4.0 with a DTD that makes tables close paragraphs implicitly in an SGML parser.
April 1998: The W3C revises HTML 4.0 without changing the DTD on the point of paragraphs and tables.
December 1999: The W3C publishes HTML 4.01 without changing the DTD on the point of paragraphs and tables.
May 2000: IE5 for Mac is released. It is the first shipping browser to have a quirks mode and a standards mode.
July 2001: A bug is filed saying that Mozilla is wrong in not making table close a paragraph implicitly and that Mozilla should start closing paragraphs in the standards mode.
October 2001: IE6 is released. It is the first version of IE for Windows that has a quirks mode and a standards mode. A table doesn’t close a paragraph in either mode.
June 2003: The Mozilla bug is fixed making Mozilla close paragraphs upon tables in the standards mode. The quirks-mode behavior is left to not closing a paragraph upon a table.
April 2005: The Web Standards Project publishes the Acid2 test made by Ian Hickson and Håkon Lie. To pass the test, a user agent must close a paragraph upon table (in the standards mode).
April 2005: In order to pass Acid2, Safari is changed to make a table close a paragraph in the standards mode. The quirks-mode behavior is left to not closing a paragraph upon a table.
May 2005: In order to pass Acid2, Opera is changed to make a table close a paragraph in the standards mode. The quirks-mode behavior is left to not closing a paragraph upon a table.
January 2006: Ian Hickson changes the comment parsing part of Acid2 and blogs about it.
February 2006: Ian Hickson publishes the first draft of the HTML5 parsing algorithm. It makes a table close a paragraph but the source code of the spec contains a comment saying “XXX quirks: don't do this”.
November 2006: IE7 is released. A table doesn’t close a paragraph in either mode.
March 2008: A preliminary version of IE8 passes Acid2 when hosted on www.webstandards.org.
February 2009: I file a spec bug requesting parsing quirks be defined.
March 2009: IE8 is released. It has four layout modes. To pass Acid2, the new ones make a table close a paragraph. The parser behavior of <p><table> is now the only HTML parsing difference between the quirks and standards modes that is interoperably implemented in all of the top 4 browser engines.
March 31st 2009: Ian Hickson asks for vendor input about parsing quirks.
April 1st 2009: I start a thread about finding vendor input in Mozilla’s platform development newsgroup. The <p><table> issue seems to be the only quirk left.
April 1st 2009: Philip Taylor uses the Validator.nu HTML Parser to compile a list of dmoz-listed pages where closing paragraph vs. not closing would lead to different parse trees.
April 21st 2009: Simon Pieters analyzes 50 sites from Philip’s list concluding that “our options regarding <p><table> parsing are (1) having the quirk, and (2) changing Acid2”.
April 22nd 2009: I check in an implementation of the quirk into the Gecko HTML5 parsing repository.
May 26th 2009: Hixie checks in the definition of the quirk into the HTML5 spec. The commit also includes this comment: “i hate myself (this quirk was basically caused by acid2; if i'd realised we could change the specs when i wrote acid2, we could have avoided having any parsing-mode quirks) -Hixie”

A big thank you to Philip Taylor and Simon Pieters for their research (both the feasibility research and the timeline research).