<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>Defining Fallback Color for RGBA</title> <style> p { padding: 25px; /* Fallback for web browsers that doesn't support RGBA */ background:rgb(0, 0, 0); /* RGBa with 0.5 opacity */ background:rgba(0, 0, 0, 0.5); } </style> </head> <body> <p><strong>Warning:</strong> This is a frist paragraph.</p> </body> </html>