define the fontSize property with a value of 20 pixels
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Style> .myFontStyle { fontSize: 20px; color: #9933FF; } </mx:Style> <mx:Button id="myButton" styleName="myFontStyle" label="Click Here" /> </mx:Application>