An element's opacity can be set using the opacity property. Values can be anywhere from 0.0 (transparent) to 1.0 (opaque).

Example Usage

<div style="opacity:0.8;">
  This is a partially transparent element
</div>

To use opacity in all versions of IE, the order is:

.transparent-element {
  /* for IE 8 & 9 */
  -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=60)"; // IE8
  /* works in IE 8 & 9 too, but also 5, 6, 7 */
  filter: alpha(opacity=60); // IE 5-7
  /* Modern Browsers */
  opacity: 0.6;
}

Syntax

Remarks

If you do not want apply opacity, you can use this instead:

background: rgba(255, 255, 255, 0.6); (opens new window)

Resources:

• MDN: https://developer.mozilla.org/en/docs/Web/CSS/opacity (opens new window);
• W3C Transparency: the ‘opacity’ property: https://www.w3.org/TR/css3-color/#transparency (opens new window)
• Browser support: http://caniuse.com/#feat=css-opacity (opens new window)