HTML/CSS "Pop-Up" Window and Disabled Background

This is a silly question since I can't find the right keywords to use to get the answer by searching Google, unfortunately.

You know when you click a link and the background dims and becomes unusable but the foreground either has an image or a sign-in box usually? Like the Yahoo mail image displaying method where everything in the background becomes grey transparent and the image itself is just fine?

How is that done? And what is it called开发者_StackOverflow中文版?

it's done by creating an overlaying div on the fly in JS, like:

var gab = document.createElement('div');
  gab.setAttribute('id', 'OVER');
  gab.innerHTML='<div class="overlay"><h1>hello</h1></div>';
  document.body.appendChild(gab);

use a CSS class like

#OVER{width:100%; height:100%; left:0;/*IE*/ top:0; text-align:center; z-index:5; position:fixed; background-color:#fff;}
.overlay {width:100%; z-index:6; left:0;/*IE*/ top:30%; font-color:#cdcdcd; font-size:0.8em; text-align:center; position:fixed; background-color:#000;}

dunno how it's called ..

You want to create a "modal box" or "lightbox". Examples:

• http://fancybox.net/
• http://www.huddletogether.com/projects/lightbox2/

thickbox

eg: http://jquery.com/demo/thickbox/

For images and stuff i use prettyphoto

For text popup Dialog

this is all done with the use of jquery a javascript

You can use smoothbox, along with mootools.