I've been practicing "parallax" sites with just CSS, and I'm posting some code pens for anyone who needs a little help.

I'm posting a link below that was given to me by another user on teamtreehouse. I know that a couple of these links are not real parallax sites. But, I think it is important for beginners to understand the background-attachment: fixed; and the background-size: cover; properties are used with parallax sites. After the user understands how to use the above two properties and their values, the user can add jQuery, or even JavaScript to make the various parts of the webpage scroll at different speeds. I hope this will help anyone who needs a little extra help learning parallax, and I just wanted to give something back to the forum, because so many people have helped me out.

http://davidwalsh.name/parallax

The above link is a good resource if your first starting out with learning how to do a, "parallax" style site.

The next two links are ones I found on my own, and both are excellent resources.

http://callmenick.com/post/simple-parallax-scrolling-effect

The one below here, is a actual parallax site, and is really broken down well. http://callmenick.com/post/advanced-parallax-scrolling-effect

Here are two codepens I've made one from the above tutorial, and one I made myself.

http://codepen.io/mike316/pen/XbjLGG

My own practice site. http://codepen.io/mike316/pen/QbGwpZ