Regular users of OpenStreetBrowser might have noticed, that there were subtle changes to the background map. This is due to a rewrite of the style sheet using MapCSS and a completely new rendering backend using pgmapcss 0.9 (a library which I developed during the last year) and Mapnik 3.0. Now, it's much easier to modify and adapt the stylesheet; also it does not need a specialiced database layout as the old did (pgmapcss supports osm2pgsql and osmosis pgsnapshot). If you have ideas for improvements or questions you can create an issue on Github or fork the style to create your own variant. Unfortunately the style (currently) is not compatible to other MapCSS renderers (e.g. JOSM).