Using jQuery you can only get the calculated value.
As an alternative, I have written a script to find the original css value by enumerating the stylesheets applied to the page, matching the selector and weighing it up by precedence and CSS specificity.
This is handy for finding out if something is auto vs. 100% vs. fixed size.
usage :
resolveAppliedStyle(document.getElementById("wrapper"), "height");
You can get the script for resolveAppliedStyle from :
https://github.com/stephen-james/FixedHeaderTable/blob/master/dependencies/lib/resolveAppliedStyle.js
and the script it uses to calculate specificity from :
https://github.com/keeganstreet/specificity/blob/master/specificity.js
