What is Mercury? Mercury is a Planet. It's also a very cool new Single-Page CSS Template
Mercury is a single-page Web site, a design approach that works very well for sites that would comprise three to six traditional pages of closely related content. A brochure site for an artist, entertainer, movie, author, or a typical restaurant would work very well. Landing pages for short-term promotions, offers and contests would too. On the other hand, a large site like Amazon.com would not be a good candidate.
A picture is worth a thousand words. Mercury comes with a pre-configured CSS class to create cool highlight boxes like this for images or callout text.