pngtile.cache: set last_modified/cache-control in 304 response as well..
#map {
overflow: hidden;
position: absolute;
top: 0px;
left: 0px;
width: 100%;
height: 100%;
}
div.leaflet-control-link {
}
a.leaflet-control-link-link {
display: block;
background-color: #fff;
box-shadow: 0 1px 5px rgba(0,0,0,0.65);
padding: 0.5em;
border-radius: 4px;
}