Blur.js is a amazing jQuery plugin for blur web elements.
It actually works by creating and placing psuedo-transparent blurred elements over the targeted ones and makes use of the StackBlur algorithm.
The source of the blurred item (it can use the background of
body or other HTML elements), radius of the effect and it is positioning can be defined with ease.
There is built-in caching for re-using the blurred image and there is support for making the item where the effect is applied to be draggable (requreis jQuery UI).
Compatibility: All Modern Browsers