Anchor Hover State
UI Item - Summary
When you hover over an anchor with your mouse, the state changes. It looks indented to provide the illusion that you're pressing a button. I like it because of that connection to the physical world. Plus, I can definitely tell if my mouse is actually over the link.
UI Item - Techniques
All that was changed was the colors and shadows of both the text and the background. I didn't notice the text shadow at first because it is subtle. What makes it indent is the inset property, which uses two different colors to differentiate the borders.