To set the opacity of an image, use the CSS -moz-opacity property. This property is used to create a transparent image in Mozilla. IE uses filter:alpha(opacity=x) to create transparent images.
Example
You can try to run the following code to style an image and set opacity with CSS:
<html> <head> </head> <body> <img style = "border:1px solid red;-moz-opacity:0.2;filter:alpha(opacity=50);" src = "https://www.tutorialspoint.com/assets/videotutorials/courses/css_online_training/380_course_215_image.jpg" /> </body> </html>