Demo Code Area - Buttons
Use Right-Click "View Source" or "Inspect" to learn
Notice the change in font color
Notice how the later styles override earlier styles in the class string
More available yet (just google it): Disabled Buttons, Button Width, Button Groups, Bordered Button Groups, Vertical Button Groups, Animated Buttons(add an arrow on hover), "pressed" effect on click, "ripple" effect on click ... all available now with CSS3 !