<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>CSS Masking: mask-image: mask with opacity</title> <link rel="author" title="CJ Ku" href="mailto:cku@mozilla.com"> <link rel="author" title="Mozilla" href="https://www.mozilla.org"> <style type="text/css"> div { position: absolute; left: 10px; top: 60px; background-color: rgba(0,0,255,0.5); width: 100px; height: 50px; } </style> </head> <body> <div></div> </body> </html>