How to make this popup window ?

How i can get this kind of a popup window to appear..

When you hover your mouse over these pictures.
http://pkmedia.wordpress.com/about/

Move your mouse over the template previews on the right, a preview window will popup.
http://www.templatemonster.com/


Any one knows how i can achieve that with my website ?

 

see http://www.dynamicdrive.com/style/csslibrary/item/css-popup-image-viewer/

 

Thanks to yesmoretrffic fo this q and thapame for this good answer. I had learned something from this post.


best wishes.
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Custom Lanyards are here.

 

thanks to thapame for ur gr8 link, i was actually searching for vertical menus.