MAPG-167 set background color

public/static/css/mapguesser.css

@@ -12,6 +12,10 @@ html, body {
     padding: 0;
 }
 
+body {
+    background-color: #cccccc;
+}
+
 button::-moz-focus-inner, input::-moz-focus-inner {
     padding: 0;
     border: 0;
@@ -374,6 +378,7 @@ header>p>span:not(:last-child) {
 }
 
 main {
+    background-color: #ffffff;
     padding: 6px 12px;
 }