Ok first up, what is CSS? (Skip to the next paragraph if you already know this.) CSS stands for Cascading Style Sheet and is the industry standard way of styling websites. If you use WordPress, every theme will have a style sheet built into it. The styling controls the look and feel of the design - the colours, the fonts, layout, spacing and so on.
A CSS Gallery (they are also known as CSS directories) is a website that showcases websites that demonstrate good design. They are a great source of inspiration if you are a web designer looking for ideas. As I discovered, they also happen to be a nice source of traffic if your site happens to get featured on one of them…