Google site search bookmarklet

Drag this link: Search this site to your bookmarks toolbar for an instant site search button. Here's the code, prettified:

function f() {
  var q=prompt('Search for');
  if (q!=null) {
    location.href='http://google.com/search?q=site:'
      + location.host + '+' + encodeURIComponent(q);
  }
}
f();