Best viewed in modern browsers. Most of these will work in WebKit based browsers only (Safari and Chrome, for example). However, not all these masks will display in both Safari and Chrome (see below). Don't forget to view the source to examine the different browser hacks required to implement masks in various browser environments.
This is a -webkit specific image mask.
Gradient image mask above. Again -webkit specific. Appears to only work in Safari, not Chrome.
SVG image mask above. Again -webkit specific. Appears to only work in Safri, not Chrome.
Text mask with background image.