I am not a lawyer, but here are some basics that apply to your situation:
Copyright attaches to any work you create as soon as it becomes fixed in a tangible medium. This means that as soon as you draw it, write it, etc., it is protected by copyright law. While the copyright law of individual countries differs, the Berne Convention establishes this immediate application of copyright as a minimum standard. So as soon as you create a website, it's covered by copyright law. Note that in the instance of a website design, copyright will really only provide you with any legal recourse if someone directly copies your work, or makes only slight modifications to it. Check out this page for an example of what I mean.
Elements you use in your website that were created by someone else are covered by their copyright ownership. Copyright is an exclusionary right, meaning that it gives the owner the right to exclude others from using the created work. So you need to get an explicit agreement from copyright holders of any images you are using in order to use them on your website, whether as part of your design or as content. A good example of this stock photography: You pay the stock photo company, and they give you the right to use their images on your site.
Trademark is a different matter. It has to do with ownership of a brand. The idea behind trademark is that it helps consumers know that when they buy something from a particular brand, it's actually made by the company that created the brand. Knockoff iPhones can damage Apple's brand, because consumers might think the knockoff is made by Apple, and if the knockoff iPhone doesn't work, they could assume Apple products are unreliable. Trademark is also different from copyright in that it is not global. Trademarks are issued at the country level.
Is the domain name you want to use already being used in another way by a brand? For example, is there a GoFast motor company, and you want to use the domain GoFast.com? If so, you'll likely run into trouble. If the domain name you want isn't going to bump into an existing trademark, you should be fine. Just buy the domain name. Domain name disputes are handled by the UDRP, which is actually pretty clear and straightforward. Basically, someone trying to use a domain name in bad faith will lose in a dispute.
There is a misconception that Creative Commons somehow routes around copyright. Instead, a CC license gives you, the copyright holder, the ability to tell the world which rights you want to allow other people to have to your work, without having to draft a license on your own (or pay a lawyer for one). If you are using CC-licensed work created by someone else, it really is imperative that you provide proper attribution. It's a courtesy to thank them for giving you something for free, and it helps reinforce CC licensing as a viable approach.
General advice: Don't try to use a name for your site or your URL that someone else is already using. It will get you into trouble. Be a good faith user of CC licensed materials, and provide attribution. Put a copyright notice at the bottom of each page of your website (this makes it clear to people that you are the person who created the site, so if they violate your copyright, you can get more out of them in court because the violation is assumed to be willful) if you want to, but clearly indicate that the content you create is available under CC license (link to the specific CC license you want to use). Don't spend time worrying about whether someone will rip off the design of your site. It's not worth it. Imagine how it would damage you if someone ripped off the design. Changes are, the effect on you would be negligible. Worry instead about making an awesome site.
