When a tile fails to load, it seems like nothing can be done to see the information in the tile beside reloading. In a case I'm looking at, reloading the page can be painful. It seems like the viewer could be more resilient to errors, like trying a second time to load a tile that failed, or skipping that tile and loading higher-res tiles in the affected area. If getting stuck trying to load a bad tile is a concern, it could wait until the user tries to zoom in deeper on the area. Is that something you would be interested in?