Before we start to write rules specific to feature types, let's have a look at styles bundled with GeoServer. You already used them when you added data in the previous chapters. Let's have a look at those documents and search for the elements we know:
Open your GeoServer administration interface at
http://localhost:8080/geoserver/web/and log in. Then select the Data | Styles item from the left menu:
Select the capitals style. The Style Editor window will open up and load the XML code:
capitals is a fairly simple example. You can see the mandatory elements required for a style. There is UserStyle with a single rule defining a circle symbol with a red fill and a black stroke.
Now try to add something wrong. Insert the following code after the
<Rule>element at line 11:<Title>This is a clever rule</Title>
Click on the Validate button. GeoServer checks your file and reports an error occurring where you inserted your code...