AlphaGraphics
AlphaGraphics is a good example of the rule of thirds. The biggest thing I noticed that makes this division obvious is the three buttons at the bottom of the page. Other elements follow this general division on the homepage, including the header and the image on the homepage.
searX
The searX website is a good example of contrast. The white-on-black colors are easy on the eyes. The logo colors stick out just enough, in spite of being mostly muted colors. Links stick out as you would expect.
Gitdab
The Gitdab website is an example of good spacing. The interface shows a dashboard for the logged in user. Everything is clearly sectioned out and easy to tap on a small screen. You can comprehend everything on the page and find what you are looking for easily.