Let the controls decide about stopPropagation and preventDefault.

src/ol/control/Navigation.js

@@ -63,6 +63,8 @@ ol.control.Navigation.prototype.zoomMap = function(evt) {
         return;
     }
     map.setZoom(map.getZoom()-delta, map.getEvents().getPointerPosition(evt));
+    // We don't want the page to scroll.
+    evt.preventDefault();
     return false;
 };
 

src/ol/control/Zoom.js

@@ -91,6 +91,13 @@ ol.control.Zoom.prototype.handle = function(evt) {
             this.map_.zoomOut();
             handled = true;
         }
+        if (handled) {
+            // Stop default behavior (i.e. don't follow link to anchor)
+            evt.preventDefault();
+            // On Android 2.3, the above does not prevent the link from being
+            // followed, but stopPropagation does.
+            evt.stopPropagation();
+        }
     }
     return !handled;
 };