User Inyerface
Since today’s topic was HTML and CSS and web design principles, you might enjoy User Inyerface, a game that demonstrates how not to design a web application. (Thanks to Kishan Patel for this recommendation.)
Although somewhat entertaining – the game demonstrates how horrible the user experience is when not following norms – remember when developing the web application for your project that even the slightest issues can lead to significant frustration. Take a few minutes to sketch your planned interface and give yourself some time for feedback from others following the application’s initial implementation. These small steps make a huge difference in the final product!