Retrieving percentage CSS values (in firefox)

This is documented:

The used value of any CSS property is the final value of that property after all calculations have been performed. Used values can be retrieved by calling window.getComputedStyle. Dimensions (e.g. width, line-height) are all in pixels... etc

There seems to be no way to access "specified" css values for a given element, unless you know exactly which css rule applies and parse out this rule using document.stylesheets or similar interface.

The correct answer is a comment on the bug I filed on bugzilla

https://bugzilla.mozilla.org/show_bug.cgi?id=707691#c7

To get the correct % value (on firefox too) the element's (or one of its parents) display should be set to none

Test : http://jsfiddle.net/4RKsM/

The unclear thing is: why on the same browser/version (see, firefox 7 on XP/win7 or Opera 11.5 on mac osx / ubuntu) but on different os, the behav is different?

Btw, the spec @thg435 posted (and reported on mdn) is still in flux.

As I know , it has never shown the percentage (I use ff, opera and chrome). So I think it's not only a firefox problem.

However, you can calculate it manually , but it is just close to the definied value , if the browser window is small.

parseInt($('#box').css('left'))/ $(window).width()*100;