Distribute requests against domains, remove unused CSS

css/app.css

@@ -62,13 +62,6 @@ input[type=text]:focus {
     border-color:#222;
 }
 
-
-#zoombuttons {
-    position:absolute;
-    right:20px;
-    top:20px;
-}
-
 #bar button {
     width:100px;
     white-space:nowrap;

js/iD/renderer/tiles.js

@@ -12,7 +12,9 @@ iD.Tiles = function(selection, projection, width, height) {
             if ((coord[2] & mask) !== 0) byte += 2;
             u += byte.toString();
         }
-        return  'http://ecn.t0.tiles.virtualearth.net/tiles/a' + u + '.jpeg?g=587&mkt=en-gb&n=z';
+        // distribute requests against multiple domains
+        var t = coord[2] % 5;
+        return  'http://ecn.t' + t + '.tiles.virtualearth.net/tiles/a' + u + '.jpeg?g=587&mkt=en-gb&n=z';
     }
 
     // derive the tiles onscreen, remove those offscreen and position tiles