opacity property specifies the opacity/transparency of an element.Transparent Image
Theopacity property can take a value from 0.0 - 1.0. The lower value, the more transparent:
opacity 0.2opacity 0.5opacity 1(default)
filter:alpha(opacity=x). The x can take a value from 0 - 100. A lower value makes the element more transparent.Example
img {
opacity: 0.5;
filter: alpha(opacity=50); /* For IE8 and earlier */} Transparent Hover Effect
Theopacity property is often used together with the :hover selector to change the opacity on mouse-over:
Example
img {
opacity: 0.5;
filter: alpha(opacity=50); /* For IE8 and earlier */}
img:hover {
opacity: 1.0;
filter: alpha(opacity=100); /* For IE8 and earlier */} Example explained
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 isopacity:1;.When the mouse pointer moves away from the image, the image will be transparent again.
An example of reversed hover effect:
Example
img:hover {
opacity: 0.5;
filter: alpha(opacity=50); /* For IE8 and earlier */} Transparent Box
When using theopacity property to add transparency to the background of an element, all of its child elements inherit the same transparency. This can make the text inside a fully transparent element hard to read:opacity 1
opacity 0.6
opacity 0.3
opacity 0.1
Example
div {
opacity: 0.3;
filter: alpha(opacity=30); /* For IE8 and earlier */} Transparency using RGBA
If you do not want to apply opacity to child elements, like in our example above, use RGBA color values. The following example sets the opacity for the background color and not the text:100% opacity
60% opacity
30% opacity
10% opacity
An RGBA color value is specified with: rgba(red, green, blue, alpha). The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).
Tip: You will learn more about RGBA Colors in our CSS3 Colors Chapter.
Example
div {
background: rgba(76, 175, 80, 0.3) /* Green background with 30% opacity */} Text in Transparent Box
This is some text that is placed in the transparent box.
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> 
