Sometimes your Internet provider will offer a free server with limited space.
For example, when I was first getting my feet wet with web development some 8 years ago, I would use the free server at Telus.net here in Western Canada. However, you cannot use your own custom domain as I had to use the prefix, "www3.telus.net/...." That was good enough for me though, seeing as I was only someone trying to learn the ins and outs of web developing. So it was just a domain for practicing the trade, but I wouldn't use it for business.