If I create a layout that a website uses, do I hold copyrights for that layout?

It depends. A lot of companies have two sets of pricing for layouts. One is a full out price to buy a layout and all its rights. That is if the buyer wants to acquire a layout that no one else will then use. These are usually pretty pricing ranging from several hundred to several thousand dollars. Then there is a cheaper option they offer where you pay to use the layout, but that is not uniquely their own. In other words the seller (you) can sell the design over and over again to different customers. So one day you may find your layout you purchased from company X on another site. These options usually are tens of dollars to a few hundred dollars.

Now in the first option you typically relinquish any right to the layout. Which is why it is costing more. The second option usually means you can keep the rights to the design and require customers to keep things like copyright logos and such on the layout.

The whole area is pretty gray though so it would be best to talk to an intellectual property lawyer if you are really concerned before you sell layouts. It all depends on the type of license you sell along with the layout. They would be able to tell you more of the specifics behind that. Usually you hold on to some rights and can post the layout on your portfolio, but not necessarily post a customer's website who is using your layout without their permission.

In other words, if I design a layout and Walmart uses it, I would often be safe to show the layout in my portfolio, but not a picture of Walmart's website using my layout if I haven't gotten permission first from Walmart... especially if they paid for the layout.

Hope that helps. :)