I think you mean copyright.
And technically, it's a creative item so any copyright is a bit redundant and would only need to be used if you can't prove the start date. Typically a domain name is enough to prove the idea.
That being said, you are mostly only copyrighting the design and programming. Reason being is that it's near impossible to prove that your website is 100% unique in it's idea.
A website could go ahead and rewrite all the functions of ebay and as long as they didn't take the code, it's not illegal.
This is why there are so many duplicate type sites out there. You have multiple ski stores, multiple payment options, multiple recipesites... You couldn't walk into another ski store and say, hey, you sell the same product, I have a copyright, you must stop now.
Doesn't work that way. You can only do it on a specific product and it's really hard to make a website a product, the only real ones I can think of are online gaming sites.
The key is to be the first or be the best, or be both.