If a website works in Firefox 4 and in Google Chrome 10, what could potentially cause that website not to work (broken layout or broken JavaScript) in IE9? What limitations and differences does IE9 have, aside from vendor-specific stylesheet rules?

Yes, that is a painfully vague question — that's because I am not asking this question from the perspective of someone with a specific problem! I'm asking this question from the perspective of someone with a working website who does not have access to IE9.


I +1ed everyone. Thanks for the great answers!


See Quirksmode.com's Compatibility Master Table (and related comparison tables) for examples of IE9's "quirky" interpretations of X/HTML and CSS.

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  • +1 I love Quirksmode's charts. Makes it easy to see where we stand with support for stuff. – John Conde Mar 14 '11 at 4:01
  • Awesome link! I had completely forgotten about that! – ClosureCowboy Mar 15 '11 at 5:24
  1. IE lags behind in support for CSS3 (CSS3 Transitions, text-shadow, CSS3 Gradients, border-image, columns)
  2. IE lags behind in support for SVG (SVG Filters)
  3. Doesn't support Web Workers
  4. Doesn't support drag-and-drop
  5. Doesn't support SVG animations
  6. Doesn't support the File API
  7. Doesn't support Geolocation (I think)
  8. Doesn't support HTML5 Forms
  9. WebGL
  10. MathML

None of these won't cause layouts to break unless you obviously decide to use them. But if you stick with conservative markup and functionality none of these will cause you any issues out of the box.

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This article has nice comparison of IE9: Is IE9 a modern browser?

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  • 1
    +1 I remember reading that when it came out. Kinda put IE9 in its place. Yeah, it's a huge step forward for Microsoft but it still needs to play catch up. Especially with their slow release cycle they need to make each update count. – John Conde Mar 14 '11 at 13:37

Among the browser comparison studies that I have seen, the caniuse.com browser comparison looks most comprehensive & updated and fits your need. The site allows you to select only two browsers at a time to compare.

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