'addRule()' Example
<html> <head> <style id="myS">.one { font-family:verdana; font-size:14pt }</style> <script language="JavaScript"> function function1() { document.styleSheets[0].addRule("div", "color:white; background-color:red;"); } </script> </head> <body> <div>This is a sample text.</div> <button onclick="function1()">Add new rule</button> </body> </html>