It's possible to know what CSS rules is applied to a specific node?
Example:
<div class="test-node">
  <strong>Test</strong>
</div>
And the CSS rules:
div           { color: blue }
div:hover     { color: green; }
.test-node    { font-weight: bold; }
div > strong  { color: red; }
So, the div node is affected by two rules div and .test-node and the div:hover if hover node only. The strong node is affected by div and div:hover rule, because it is inner a div, but the color property is overwrited by your own rule div > strong (example http://jsfiddle.net/yyf9v/).
Basically I need discovery how I can do the samething that Chrome Inspector does in javascript. If you use Chrome, go to Inspector (CTRL + Shift + J, Elements and select a node). You will se a Styles tab, that show element.style rule (attribute style basically) and the Matched CSS Rules... I need this!