CSS Image Opacity / Transparency
Creating transparent images with CSS is easy.
The CSS opacity property is a part of the CSS3 recommendation.
Example 1 - Creating a Transparent Image
The CSS3 property for transparency is opacity.
First we will show you how to create a transparent image with CSS.
Regular image:
The same image with transparency:
Look at the following CSS:
Example
img
{
   
opacity: 0.4;
   
filter: alpha(opacity=40); /* For IE8 and earlier */
}
Try it Yourself »
The opacity property can take a value from 0.0 - 1.0. The lower value, 
the more transparent.
IE8 and earlier use filter:alpha(opacity=x). The x can take a value from 0 - 100. A lower value makes the element more transparent.
Example 2 - Image Transparency - Hover Effect
Mouse over the images:
The CSS looks like this:
Example
img
{
   
opacity: 0.4;
   
filter: alpha(opacity=40); /* For IE8 and earlier */
}
img:hover
{
   
opacity: 1.0;
   
filter: alpha(opacity=100); /* For IE8 and earlier */
}
Try it Yourself »
The first CSS block is similar to the code in Example 1. In addition, we have added 
what should happen when a user hovers over one of the images. In this case we want the image to NOT be 
transparent when the user hovers over it. The CSS for this is opacity:1;.
When the mouse pointer moves away from the image, the image will be transparent again.
Example 3 - Text in Transparent Box
This is some text that is placed in the transparent box.
The source code looks like this:
Example
<html>
<head>
<style>
div.background
  {
      background: url(klematis.jpg) repeat;
   
   
  border: 2px solid black;
  }
div.transbox
  {
   
   
  margin: 30px;
      background-color: #ffffff;
   
   
  border: 1px solid black;
      opacity: 0.6;
   
   
  filter: alpha(opacity=60); /* For IE8 and earlier */
  }
	
div.transbox p
  {
     
  margin: 5%;
   
   
  font-weight: bold;
      color: #000000;
  }
</style>
</head>
<body>
<div class="background">
 
<div class="transbox">
   
<p>This is some text that is placed in the transparent box.</p>
 
</div>
</div>
</body>
</html>
Try it Yourself »
First, we create a <div> element (class="background") with a background image, and a border. Then we create another <div> (class="transbox") inside the first <div>. The <div class="transbox"> have a background color, and a border - the div is transparent. Inside the transparent <div>, we add some text inside a <p> element.

