As Steve pointed out, this is does deserve two exclamation points!!

Just like CSS for styling web pages, GSS is a specification for designing maps. Adapted for dynamic data sources, GSS can define changing geographic elements, display multiple datasets, and even respond to contextual tags like “condition:poor”.

Very tasty! Just look at this simple GSS and how you can render maps on the client.

body: {
fillStyle: "#fff",
lineWidth: 0,
},

node: {
fillStyle: "#ddd",
strokeStyle: "#090",
lineWidth: 0,
radius: 1
},

way: {
strokeStyle: function() {
return "rgba(1,1,1,0.7)"
//return color_from_string(this.user)
},
strokeStyle: "#ccc",
lineWidth: 3
},

leisure: {
fillStyle: "#2a2",
lineWidth: 3,
strokeStyle: "#181"
}

Previous conversation about styling GIS data.