An element, perhaps a navigation bar, that resides somewhere down the page. The user scrolls the page and once the element hits the top of the page it sticks, so it's always visible.
A list where each list element has three columns. Content within each column is centered vertically.
A navigation list. Clicking on a main link opens a sub-level of navigation, while hiding any other sections that are currently open.
A mixin for formatting prices a little easier.