JQuery :: CSS Function Reports Value Of Clip Inconsistently

Given: a CSS definition of this sort:
div {clip:rect(0px 30px 30px 0px); /*(values set arbitrarily) */ }

Using IE 8, if I attempt the following:
$(document).ready(function () { alert( $("div").css("clip") ) });

The alert reports "undefined" unless the clip is defined in an inline style, i.e.
<div style="clip:rect(...);"></div>.

When the style is inline, it returns space-separated values, e.g. "rect(0px 30px 30px 0px)," even if the clip is defined with comma-separated values. In FireFox 3.6.12 Mac, the alert reports "auto" if the clip is defined inline, but returns a string with comma-separated values (even if the definition uses space-separated values) if the clip is defined in a <style> tag. WebKit browsers (tested on Safari 5.0.2 and Chome 7.0) return space-separated values of clip no matter if it is defined inline or in a style tag, and no matter if the definition contains commas or not.