Edit in JSFiddle

<img id="css-filter-blur" src="http://css-plus.com/examples/2012/03/gaussian-blur/i/fence.jpg" alt="Blur" height="200" width="300" />

#css-filter-blur { margin: 20px; }
#css-filter-blur:hover { 
    -webkit-filter: blur(2px); 
    -moz-filter: blur(2px); 
    filter: blur(2px); 
}