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New Doctype Sniffing In Upcoming Mozilla Releases

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Bill Mason

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User since: 10 Oct 2000

Articles written: 5

The Mozilla browser, like several other browsers on the market, uses DOCTYPE sniffing to determine how to render a page. In Mozilla's case, it either renders the page strictly, in "standards mode," or more loosely -- otherwise known as "quirks mode." Now Mozilla introduces something more.

Almost Standards

In the upcoming 1.01 and 1.1 releases, Mozilla will add an "almost standards" mode to its mix. This mode is virtually identical to the standards mode (now being referred to as "full standards mode") but with one crucial change. In almost standards mode, Mozilla will not implement the CSS-2 line-height rules that causes many pages with pixel-precise image layouts via tables to break apart.


Several DOCTYPEs that formerly triggered full standards mode will now render in almost standards mode. Those DOCTYPEs are:

  • XHTML 1.0 Transitional
  • XHTML 1.0 Frameset
  • HTML 4.01 Transitional with a system identifier URL in the DOCTYPE
  • HTML 4.01 Frameset with a system identifier URL in the DOCTYPE
  • One particular system DOCTYPE as a concession to some specific needs of IBM (all other system DOCTYPEs render in full standards mode).

Reference material

Front-end web development (mostly) and an interest/focus in web accessibility. I also recently co-authored my first book, The Web Professional's Handbook, published by the late great glasshaus.

I've been out of work since October 2001. Be kind and glance over my portfolio....

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