DOM Enlightenment Book
HTML
<script src="https://getfirebug.com/firebug-lite-debug.js"></script>
<style id="styleElement">
p{line-height:1.4em; color:blue;} /*index 0*/
p{font-size:50px;} /*index 1*/
</style>
<p>Hi</p>
JavaScript
//add a new CSS rule at index 1 in the inline style sheet
document.querySelector('#styleElement').sheet.insertRule('p{color:red}',1);
//verify it was added
console.log(document.querySelector('#styleElement').sheet.cssRules[1].cssText);
//Delete what we just added
document.querySelector('#styleElement').sheet.deleteRule(1);
//verify it was removed
console.log(document.querySelector('#styleElement').sheet.cssRules[1].cssText);