Block user interface

The use of a transparent DIV is common in the Web 2.0  jQuery Block UI is a jQuery Plugin that help us with it.
It's easy to easy, to block all the page we can put this code:

$.blockUI();

and this one to remove the block:

$.unblockUI();

If we like to block/unblock all jQuery ajax request:

$().ajaxStart($.blockUI).ajaxStop($.unblockUI);

To block a specific element in the page, select it: 

$('div.test').block();

jQuery Block UI allows has to change the message, the color, the fadein/out effect, to open a modal dialog, the overlay color, the CSS etc.

Personally I like to use with the events beginRequest Event and endRequest Event of Asp.net Ajax.

P.S. it doesn't work well with a pages including IFRAME.