about AJAX?

It's quite simple to do.

You just add two div's to your code and set their style property to be hidden. The first div will serve as the block you want to highlight, such as confirmation window (do you want to delete? yes/no). The other will be the white, gray, black, whatever background.

When on you click on a link or something, you merely change the 'hidden' style to 'block' with a javascript. This will create the effect of a popup window.

Here's the code to that:

var myDiv = document.getElementById('x');

myDiv.style.display = "block";

// where x is my div's name

To remove the effect just set the display property to hidden again:

myDiv.style.display = "hidden";

In order for the background to look "shaded" you set the second div's opacity like so:

style='filter: alpha(Opacity=50);opacity: 0.5;'

I think this is called Spotlight effect... Many frameworks have built in support for this. Scriptaculos and JQuery will have this kind of feature.

You can achieve this in the following steps...

1)Have a div that spans from 0,0 to max_width, max_height of the window object. Make visibility to hidden at first.

2) Color the div to have white background and set the transparency to have that effect.

3) On click of link(thumbnail in this case), bring the div to front and using ajax or even creating a new img object and the browser will pull the image from image source.

4)Have a close button in div which will set the visibility of div to hidden and visibility of parent layer to true.

This is not AJAX -(Asynchronous Java Script and XML)...

Ajax is done in order to reduce the round trip time from client to server. In that they will use a middle level server,Ajax server.....

Your scenario happens by the use of javascript or vb script and call of some function from the jsp or asp page.

i think thats more of html codes plus scripts.