Короткий и практичный пример.
CSS:
.blur {
filter: blur(3px); -webkit-filter: blur(3px); -moz-filter: blur(3px);
-o-filter: blur(3px); -ms-filter: blur(3px);
filter: url(blur.svg#blur);
}
Использовать можно так:
<body class="blur">
Так же хороший вариант предложил Вадим, могу сказать, что CSS3 класс работет. Для будущих читательей размещу код здесь, на случай исчезновения ссылки:
.css3-gaussian-blur *
{
text-shadow: 0 0 10px rgba(0, 0, 0, .5) !important;
color: transparent !important;
background-image: none !important;
border-color: rgba(0, 0, 0, .05) !important;
/* disable the pointer events for blurred zones */
-moz-pointer-events: none !important;
-webkit-pointer-events: none !important;
pointer-events: none !important;
}
.css3-gaussian-blur input,
.css3-gaussian-blur textarea,
.css3-gaussian-blur button,
.css3-gaussian-blur select
{
box-shadow: 0 0 10px rgba(0, 0, 0, .5) !important;
border-color: rgba(0, 0, 0, .05) !important;
resize: none !important;
opacity: .5 !important;
}
.css3-gaussian-blur img,
.css3-gaussian-blur input,
.css3-gaussian-blur input[type="file"],
.css3-gaussian-blur input[type="checkbox"],
.css3-gaussian-blur input[type="radio"]
.css3-gaussian-blur textarea,
.css3-gaussian-blur select
{
opacity: .2 !important;
background: transparent none !important;
}
.css3-gaussian-blur fieldset
{
border-color: transparent !important;
}
/* Vendor-specific styles */
/* CSS3 filters are currently supported by Chrome only */
@media screen and (-webkit-min-device-pixel-ratio:0) {
.css3-gaussian-blur img
{
-webkit-filter: blur(15px) !important;
filter: blur(15px) !important;
opacity: 1 !important; /* restore the opacity for that browser */
}
}
/* IE<10 styles using the \9 hack */
.css3-gaussian-blur img
{
filter: progid:DXImageTransform.Microsoft.Blur(pixelradius=20)\9 !important; /* IE has native support for filters since version 5.5 */
-ms-filter: progid:DXImageTransform.Microsoft.Blur(pixelradius=20)\9 !important; /* IE has native support for filters since version 5.5 */
opacity: 1\9 !important;
}
.css3-gaussian-blur *
{
color: #ccc !important\9;
}
Использовать можно так:
<body class="css3-gaussian-blur"> 
Простой
Простой