I am wondering what is Quirks mode in IE8 Developer toolbar? Why page rendering is different in Quirks mode than in IE8 standard mode?
3 Answers
Simply speaking, it is for really old webpages to show in the way it always has been on IE. So if a webpage's HTML doesn't start with a DOCTYPE that indicates Standard Compliance Mode, then IE will show it in Quirks mode. In such mode, IE uses its own Box Model to render the page elements.
A simple example is: IE's box model adds padding to the inside of the width, so a div occupies the width number of pixels, but Standard Compliance mode add the padding to the width, so a div will occupy width + padding number of pixels.
You can try a div with width 300px and padding 100px and click between the modes in IE Developer's bar to see the difference.
More info at: http://en.m.wikipedia.org/wiki/Quirks_mode

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I think it will be useful : http://www.quirksmode.org/css/quirksmode.html.

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Quirks mode is basically a legacy mode that allows IE to render web pages that were written back in the day where no one adhered to html standards.

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