I'm currently reviewing the HTML and CSS code for a website at http://preview.python.org/ but there are some things I don't quite grasp. One thing that caught my eye is the search-box - how did they achieve the icon-search feature? I doubt it's just a simple image file like a jpg or png, so how exactly was it created? Another interesting element is how the input box extends from right to left when you focus on it. My tests with other input boxes didn't yield the same result. Can someone shed some light on how this effect is achieved? Any help would be greatly appreciated.