Here’s something for beginner CSS. Fitting two divs right next to each other, without an empty space between. Here’s an example:
I see it all the time, people just creating designs that look nice and shoving them up not giving any consideration to how users will interact with that oh so special design they made for the their clients. From experience I’ve noticed how people don’t really care about design that much but more how easy it is to use the site and do the tasks they went on the website to accomplish. Look at Facebook for instance, no one goes on there and compliments how well designed it is but you rarely hear a complaint about how people can’t find where someones photos are or how they can’t see updates from their friends.