Real78,
It is fairly easy to copy the basic design of a website once you have all of the documents that are used to render it. If it is a template you are copying, take the source code of the page you are looking at. Then you will want all of the CSS and/or JS files that are being requested on that page. Note that this is a very tedious process. Reverse engineering how someone built a website can be just as time consuming as building one from scratch. It will also help if you are already a decent programmer.
If you have access to dreamweaver, this tutorial talks about how to copy a web page,
http://www.ehow.com/how_6177982_copy-dreamweaver.html
Hope that helps,
Shawn