docfix/Tweak branding.md document

Author: constantine2nd

branding.md

@@ -4,10 +4,46 @@ Look and feel of the API landing page can be modified via css and with a number
 
 ## CSS
 
-The default css is located here:
+### Main CSS
+
+The main css is located here:
 
 OBP-API/src/main/webapp/media/css/website.css
 
+In case you want to keep it outside of the public code you can specify a new URI via props `webui_main_style_sheet`. For instance:
+
+webui_override_style_sheet = https://static.openbankproject.com/test/css/website.css
+
+### Override CSS
+
+The override css is used if you use `OBP-API/src/main/webapp/media/css/website.css` but you want to override some instance specific values.
+In that case you can do it via props `webui_override_style_sheet` i.e.
+
+webui_override_style_sheet = https://static.openbankproject.com/test/css/override.css
+
+where `override.css` could be:
+
+```css
+.navbar-default .navbar-nav > li #navitem-logo {
+    padding-top: 11px;
+    padding-bottom: 11px;
+    margin-right: 16px;
+    height: 88px;
+    margin-left: 0;
+}
+
+.navbar-default .navbar-nav > li #navitem-logo img {
+	width: 67px;
+	height: 67px;
+}
+
+
+
+#main-about {
+    height: 552px;
+}
+```
+
 ## Props
 
 There's a number of props variables starting with webui_* - see OBP-API/src/main/resources/props/sample.props.template for a comprehensive list and default values.