One of my favorite reference apps for BlackBerry 10 has got a small update and includes a half price sale. Web Design Cheat Sheet is an awesome reference app for anyone wanting some HTML/CSS knowledge. It includes syntax and includes fairly detailed notes to explain each of them. There is even a resource section for further reading. It also includes video tutorials and an editor and preview mode.
You can check out our hands on to see how the app works. Otherwise, give it a download using the link below. It is free to download and the HTML section is free.