- The very first feature of custom buttons is that everything inside them has been treated as inline element. The left/right borders of buttons are rendered on outer element, while the top/bottom borders are rendered on the inner element.
- You can now change the skin of the buttons with just few lines of CSS, which is definitely going to be a key factor after the introduction of Gmail themes.
- Affordances are built for changing the color of the border on hover. The gradient direction is reversed for achieving that active/click state that will make it feel like you are pressing the button actually.
Don’t get so fascinated by the trick. You can also develop custom buttons yourself. Douglas Bownman has described how he came up with introducing Google’s custom buttons, that are used in Gmail and other applications. As custom interfaces often provide a good look and better feel, lots of designers are surely going to find these open source buttons really useful.