Default unit is pixels

            
<?xml version="1.0"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
    <mx:Style>
        .myFontStyle { 
           fontSize: 20px; 
           color: #9933FF; 
        }
        .myOtherFontStyle { 
           fontSize: 20; 
           color: #9933FF; 
        }
    </mx:Style>
    <mx:Button id="myButton" styleName="myFontStyle" label="Click Here" />
    <mx:Button id="myButton2" styleName="myOtherFontStyle" label="Click Here" />
</mx:Application>

Related examples in the same category

1.	CSS Inline
2.	CSS Style Tag
3.	CSS like Styles
4.	Styles with Namespace
5.	Flex CSS: class definitions that work the same way as HTML CSS
6.	Using CSS to apply graphical skins
7.	Apply dropShadowEnabled to CSS
8.	CSS over write
9.	Add CSS for Application
10.	CSS class with namespace and without namespace
11.	Changing CSS Selectors
12.	CSS Type Selector
13.	Embeds an image in CSS
14.	Define the mySize variable and uses it in the CSS
15.	To specify an Array for the fills property in CSS, you use a comma-separated list
16.	Show how to use CSS class selectors to set the labelPosition and other properties that affect the appearance of data labels in a chart
17.	Two Spark Button controls inherit the styles of the Group descendant selector
18.	Using Spark namespace for the Button components and the MX namespace for the Box containers
19.	Using 9-slice properties
20.	Numeric Format Color Value
21.	Color Format Inline
22.	CamelCase vs hyphen
23.	Use tag, set the styles using CSS syntax
24.	CSS hexadecimal format for CSS style definitions and tag support
25.	Loading style sheets defined in CSS at run time
26.	Adding global CSS styles
27.	When you use the tag, you set the styles by using CSS syntax or a reference to an external file that contains style declarations, as the following example shows:
28.	The following example sets styles by using CSS on the Legend control:
29.	Apply style with CSS
30.	CSS style vs Control property style setting
31.	Use CSS to Style Components
32.	Embed Styles by Using CSS
33.	Change CSS style at runtime
34.	TextInput CSS style
35.	CSS style by ID

Default unit is pixels : CSS « Style « Flex

Related examples in the same category